Systems and methods for multi-orientation flight

ABSTRACT

A method of operating an unmanned aerial vehicle (UAV) includes generating, with aid of one or more processors, a signal that causes the UAV to flip from a first orientation to a second orientation opposite to the first orientation, and effecting, with aid of one or more propulsion units, flip of the UAV from the first orientation to the second orientation in response to the signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/245,946, filed on Jan. 11, 2019, which is a continuation ofInternational Application No. PCT/CN2016/089818, filed on Jul. 12, 2016,the entire contents of both of which are incorporated herein byreference.

BACKGROUND

Aerial vehicles such as unmanned aerial vehicles (UAVs) have a widerange of real-world applications including surveillance, reconnaissance,exploration, logistics transport, disaster relief, aerial photography,large-scale agriculture automation, live video broadcasting, etc. Insome instances, an orientation of a UAV may be disrupted due to variousfactors such as severe weather conditions, collision with another objector the terrain, or malfunction of the UAV. This can cause the UAV to bein an upside position during flight or after a crash. In most cases, theUAV may not be capable of flight and/or taking off from an upside downposition or an inclined position. A user may need to manually change theorientation of the UAV to a right-side up position to permit the UAV totake off. This may be inconvenient for users to re-launch the UAV,particularly when the UAV is far away from the user, or at some locationthat is unknown to the user or inaccessible to the user.

SUMMARY

A need exists for improved systems and methods for flight of aerialvehicles, such as unmanned aerial vehicles (UAVs). Multi-orientationflight may be provided for aerial vehicles, which may permit the UAV thetakeoff, land, or fly the UAV in different orientations. For instance,the UAV may be capable of flight in both a first orientation and asecond orientation. In some embodiments, the first orientation and thesecond orientation may be laterally opposite to each other. For example,in some cases, the UAV may be upside down when it is in the firstorientation, and the UAV may be right side up when it is in the secondorientation. The UAV may be capable of accommodating differentorientations for flight, by altering the direction and/or speed ofrotation of one or more propulsion units of the UAV to change thedirection in which the lift force is being generated. One or moreelectronic speed control (ESC) units may aid in the changing of thedirection and/or speed of rotation of the propulsion units. In someembodiments, the propulsion units may be protected by one or moreprotective covers. The protective covers can be used to protect one ormore components of the propulsion units from impact with an externalsurface. The components of the propulsion units may include rotor bladesand/or actuators (such as motors). The use of protective covers maypermit the UAV to land on a landing surface without damage to thepropulsion units. This may be particularly useful in crash landingsituations where the orientation in which the UAV lands on a surface maybe unknown. The systems and methods described herein may permit the UAVto take off from a landing surface, regardless of an orientation of theUAV on the surface. The landing surface can be a flat surface, inclinedsurface, or curved surface. In some instances, the landing surface maybe a rough surface having undulating terrain.

In one aspect of the present disclosure, a method of operating anunmanned aerial vehicle (UAV) is provided. The method may comprise:providing a signal to control one or more corresponding propulsionunits, thereby controlling directions of rotation of a first set ofrotating components and a second set of rotating components of the oneor more propulsion units, wherein the first set of rotating componentsare configured to rotate in a first direction and the second set ofrotating components are configured to rotate in a second direction whenthe UAV is in a first orientation, and the first set of rotatingcomponents are configured to rotate in the second direction and thesecond set of rotating components are configured to rotate in the firstdirection when the UAV is in a second orientation opposite the firstorientation; and protecting the one or more propulsion units with one ormore protective covers that prevent the propulsion units from directlycontacting an external object.

In some embodiments, the method may further comprise controlling thedirections of the first and second sets of rotating components of theone or more propulsion units to generate a lift for the UAV. In someembodiments, the method may further comprise generating the lift whenthe UAV is taking off from an underlying surface when the UAV is in thefirst orientation or the second orientation. In some cases, a height ofthe one or more protective covers is greater than a height of a body ofthe UAV. In some cases, a height of the one or more protective covers isgreater than a height of the one or more propulsion units. In somecases, a first portion of the one or more protective covers is incontact with an underlying surface when the UAV is in the firstorientation, and a second portion of the one or more protective coversis in contact with the underlying surface when the UAV is in the secondorientation. In some cases, the first and second portions of the one ormore protective covers are laterally opposite to each other relative toa horizontal plane passing through a body of the UAV. In some cases, thesecond portion is located above the body in a direction of liftgenerated by the one or more propulsion units when the UAV is in thefirst orientation. In some cases, the first portion is located above thebody in a direction of lift generated by the one or more propulsionunits when the UAV is in the second orientation.

In some cases, each of the one or more protective covers forms a tunnelaround a corresponding propulsion unit of the one or more propulsionunits. In some cases, each protective cover comprises a sleeve in whicha propulsion unit is disposed. In some cases, the one or more protectivecovers permit the one or more rotating components of the one or morepropulsion units to rotate in the first direction or the seconddirection when the UAV is on an underlying surface. In some cases, thesignal is provided to the one or more corresponding propulsion units byone or more electrical signal control (ESC) units, said ESC unitsconfigured to individually control speeds of one or more correspondingrotating components of the one or more propulsion units. In some cases,the signal from the one or more ESC units is configured to cause the UAVto change orientations between the first orientation and the secondorientation. In some cases, the one or more rotating components includerotor blades.

In some cases, the first orientation is for the UAV to be upside down.In some cases, the second orientation is for the UAV to be right-sideup. In some cases, the UAV is capable of taking off from an underlyingsurface in the first orientation and in the second orientation. In somecases, the UAV is capable of hovering or flight when in the firstorientation and in the second orientation. In some cases, the one ormore protective covers serve as landing gears for the UAV.

In another aspect of the present disclosure, an unmanned aerial vehicle(UAV) is disclosed herein. The UAV may comprise: one or more propulsionunits configured to generate lift for the UAV, the one or morepropulsion units comprising a first set of rotating components and asecond set of rotating components, wherein the first set of rotatingcomponents are configured to rotate in a first direction and the secondset of rotating components are configured to rotate in a seconddirection when the UAV is in a first orientation and the first set ofrotating components are configured to rotate in the second direction andthe second set of rotating components are configured to rotate in thefirst direction when the UAV is in a second orientation opposite thefirst orientation; one or more one or more processors, wherein one ormore processors are configured to individually or collectively controldirection of the first set of rotating components and the second set ofrotating components of the one or more propulsion units; and one or moreprotective covers that prevent the one or more propulsion units fromdirectly contacting an external object.

In some cases, the lift may be generated when the UAV is taking off froman underlying surface when the UAV is in the first orientation or thesecond orientation. In some cases, a height of the one or moreprotective covers is greater than a height of a body of the UAV. In somecases, a height of the one or more protective covers is greater than aheight of the one or more propulsion units. In some cases, a firstportion of the one or more protective covers is in contact with anunderlying surface when the UAV is in the first orientation, and asecond portion of the one or more protective covers is in contact withthe underlying surface when the UAV is in the second orientation. Insome cases, the first and second portions of the one or more protectivecovers are laterally opposite to each other relative to a horizontalplane passing through a body of the UAV. In some cases, the secondportion is located above the body in a direction of lift generated bythe one or more propulsion units when the UAV is in the firstorientation. In some cases, the first portion is located above the bodyin a direction of lift generated by the one or more propulsion unitswhen the UAV is in the second orientation.

In some cases, each of the one or more protective covers forms a tunnelaround a corresponding propulsion unit of the one or more propulsionunits. In some cases, each protective cover comprises a sleeve in whicha propulsion unit is disposed. In some cases, the one or more protectivecovers permit the one or more rotating components of the one or morepropulsion units to rotate in the first direction or the seconddirection when the UAV is on an underlying surface. In some cases, theone or more processors are located in one or more ESC units or a flightcontroller. In some cases, a signal from the one or more processors isconfigured to cause the UAV to change orientations between the firstorientation and the second orientation. In some cases, the one or morerotating components include rotor blades.

In some cases, the first orientation is for the UAV to be upside down.In some cases, the second orientation is for the UAV to be right-sideup. In some cases, the UAV is capable of taking off from an underlyingsurface in the first orientation and in the second orientation. In somecases, the UAV is capable of hovering or flight when in the firstorientation and in the second orientation. In some cases, the one ormore protective covers serve as landing gears for the UAV.

In another aspect of the present disclosure, a method of operating anunmanned aerial vehicle (UAV) is provided herein. The method maycomprise: generating, with aid of one or more processors, a signal thatcauses the UAV to flip from a first orientation to a second orientationopposite the first orientation; and effecting, with aid of one or morepropulsion units, the flip of the UAV from the first orientation to thesecond orientation in response to the signal.

In some cases, the UAV is flipped from the first orientation to thesecond orientation opposite the first orientation while the UAV is on anunderlying surface. In some cases, the methods further comprisingobtaining data indicative of a user input to initiate the flip of theUAV from the first orientation to the second orientation. In some cases,the user input is received at a terminal remote to the UAV. In somecases, the terminal transmits the user input to the UAV via a wirelessconnection. In some cases, the methods further comprising obtaining datafrom one or more sensors to initiate the flip of the UAV from the firstorientation to the second orientation. In some cases, the one or moresensors are on-board the UAV. In some cases, the one or more sensorsdetect an orientation of the UAV. In some cases, the first orientationof the UAV is to be upside down. In some cases, the second orientationof the UAV is to be right side up.

In some cases, the UAV comprises one or more protectors that prevent theone or more propulsion units from directly contacting the underlyingsurface. In some cases, the UAV is on the underlying surface for atleast a moment in time after flipping to the second orientation. In somecases, the methods further comprising effecting, with aid of the one ormore propulsion units, takeoff of the UAV from the underlying surfacesubsequent to the flip of the of the UAV from the first orientation tothe second orientation. In some cases, the methods further comprisingeffecting flight of the UAV in the second orientation. In some cases,the UAV is flipped from the first orientation to the second orientationopposite the first orientation when one or more sensors detect that theUAV has reached a threshold condition. In some cases, the one or moresensors are onboard the UAV. In some cases, the one more sensors areconfigured to detect whether the UAV has reached the threshold conditionwhen the UAV is in flight. In some cases, the threshold condition isreached during flight of the UAV. In some cases, the threshold conditionis an altitude of the UAV with respect to the underlying surface. Insome cases, the threshold condition is a velocity or acceleration of theUAV with respect to the underlying surface. In some cases, the velocityor acceleration is a vertical velocity or acceleration of the UAV withrespect to the underlying surface. In some cases, the thresholdcondition is power provided to the one or more propulsion units, orpower consumed by the one or more propulsion units. In some cases, thethreshold condition is an amount of time that has elapsed since the UAVhas taken off from the underlying surface. In some cases, the one ormore sensors are on-board the UAV. In some cases, the one or morepropulsion units permit the UAV to take off from the underlying surfaceregardless of orientation of the underlying surface relative to thedirection of gravity. In some cases, the first orientation is for theUAV to be upside down. In some cases, the second orientation is for theUAV to be right side up.

In some cases, the UAV comprises one or more protectors that prevent theone or more propulsion units from directly contacting the underlyingsurface. In some cases, the signal is indicative of a user input toinitiate the flip of the UAV. In some cases, the user input is providedvia a user terminal remote to the UAV. In some cases, the signal isgenerated at the user terminal and transmitted via one or morecommunication channels from the user terminal to the UAV. In some cases,the user input to initiate the flip is only capable of initiating theflip and no other actions by the UAV. In some cases, the flip of the UAVfrom the first orientation to the second orientation causes a change inat least 170 degrees of the orientation of the UAV. In some cases, theuser input is a single action that effects the flip of the UAV from thefirst orientation to the second orientation. In some cases, the singleaction is the selection of a button or touchscreen of a terminal remoteto the UAV. In some cases, the single action is the flip of a switch ona terminal remote to the UAV. In some cases, the single action is averbal command that is registered by a terminal remote to the UAV. Insome cases, the single action is a change in attitude of a terminalremote to the UAV. In some cases, the signal indicative of the userinput is obtained while the UAV is on an underlying surface. In somecases, the signal indicative of the user input is obtained while the UAVis in flight. In some cases, the first orientation is for the UAV to beupside down. In some cases, the second orientation is for the UAV to beright side up. In some cases, the UAV comprises one or more protectorsthat prevent the one or more propulsion units from directly contactingthe underlying surface.

In yet another aspect of the present disclosure, an unmanned aerialvehicle (UAV) is disclosed herein. The UAV may comprise: one or moreprocessors, individually or collectively configured to generate a signalthat causes the UAV to flip from a first orientation to a secondorientation opposite the first orientation; and one or more propulsionunits that effect the flip of the UAV from the first orientation to thesecond orientation in response to the signal.

In some cases, the flip of the UAV from the first orientation to thesecond orientation opposite the first orientation is while the UAV is onan underlying surface. In some cases, the one or more processors isconfigured to obtain data indicative of a user input to initiate theflip of the UAV from the first orientation to the second orientation. Insome cases, the user input is received at a terminal remote to the UAV.In some cases, the terminal transmits the user input to the UAV via awireless connection. In some cases, the one or more processors areconfigured to obtain data from one or more sensors to initiate the flipof the UAV from the first orientation to the second orientation. In somecases, the one or more sensors are on-board the UAV. In some cases, theone or more sensors detect an orientation of the UAV. In some cases, thefirst orientation of the UAV is to be upside down. In some cases, thesecond orientation of the UAV is to be right side up.

In some cases, the UAV comprises one or more protectors that prevent theone or more propulsion units from directly contacting the underlyingsurface. In some cases, the UAV is on the underlying surface for atleast a moment in time after flipping to the second orientation. In somecases, the one or more propulsion units is configured to effect, withaid of the one or more propulsion units, takeoff of the UAV from theunderlying surface subsequent to the flip of the of the UAV from thefirst orientation to the second orientation. In some cases, the one ormore propulsion units are configured to effect effecting flight of theUAV in the second orientation. In some cases, the flip of the UAV fromthe first orientation to the second orientation opposite the firstorientation is when one or more sensors detect that the UAV has reacheda threshold condition. In some cases, the one or more sensors areonboard the UAV. In some cases, the one more sensors are configured todetect whether the UAV has reached the threshold condition when the UAVis in flight. In some cases, the threshold condition is reached duringflight of the UAV. In some cases, the threshold condition is an altitudeof the UAV with respect to the underlying surface. In some cases, thethreshold condition is a velocity or acceleration of the UAV withrespect to the underlying surface. In some cases, the velocity oracceleration is a vertical velocity or acceleration of the UAV withrespect to the underlying surface. In some cases, the thresholdcondition is power provided to the one or more propulsion units, orpower consumed by the one or more propulsion units. In some cases, thethreshold condition is an amount of time that has elapsed since the UAVhas taken off from the underlying surface. In some cases, the one ormore sensors are on-board the UAV. In some cases, the one or morepropulsion units permit the UAV to take off from the underlying surfaceregardless of orientation of the underlying surface relative to thedirection of gravity. In some cases, the first orientation is for theUAV to be upside down. In some cases, the second orientation is for theUAV to be right side up.

In some cases, the UAV comprises one or more protectors that prevent theone or more propulsion units from directly contacting the underlyingsurface. In some cases, the signal is indicative of a user input toinitiate the flip of the UAV. In some cases, the user input is providedvia a user terminal remote to the UAV. In some cases, the signal isgenerated at the user terminal and transmitted via one or morecommunication channels from the user terminal to the UAV. In some cases,the user input to initiate the flip is only capable of initiating theflip and no other actions by the UAV. In some cases, the flip of the UAVfrom the first orientation to the second orientation causes a change inat least 170 degrees of the orientation of the UAV. In some cases, theuser input is a single action that effects the flip of the UAV from thefirst orientation to the second orientation. In some cases, the singleaction is the selection of a button or touchscreen of a terminal remoteto the UAV. In some cases, the single action is the flip of a switch ona terminal remote to the UAV. In some cases, the single action is averbal command that is registered by a terminal remote to the UAV. Insome cases, the single action is a change in attitude of a terminalremote to the UAV. In some cases, the signal indicative of the userinput is obtained while the UAV is on an underlying surface. In somecases, the signal indicative of the user input is obtained while the UAVis in flight. In some cases, the first orientation is for the UAV to beupside down. In some cases, the second orientation is for the UAV to beright side up. In some cases, the UAV comprises one or more protectorsthat prevent the one or more propulsion units from directly contactingthe underlying surface.

It shall be understood that different aspects of the present disclosuremay be appreciated individually, collectively, or in combination witheach other. Various aspects of the present disclosure described hereinmay be applied to any of the particular applications set forth below orfor any other types of UAVs. Any description herein of an aerial vehiclemay apply to and be used for any UAV, such as any vehicle. Additionally,the devices and methods disclosed herein in the context of aerial motion(for example, flight) may also be applied in the context of other typesof motion, such as movement on the ground or on water, underwatermotion, or motion in space. Other objects and features of the presentdisclosure will become apparent by a review of the specification,claims, and appended figures.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety.

BRIEF DESCRIPTION

The novel features of the present disclosure are set forth withparticularity in the appended claims. A better understanding of thefeatures and advantages of the present disclosure will be obtained byreference to the following detailed description that sets forthillustrative embodiments, in which the principles of the presentdisclosure are utilized, and the accompanying drawings of which:

FIG. 1 shows an example of an unmanned aerial vehicle (UAV) capable offlight in multiple orientations, in accordance with embodiments of thepresent disclosure.

FIG. 2 shows a schematic view of a UAV changing its orientation on ahorizontal landing surface, in accordance with embodiments of thepresent disclosure.

FIG. 3 shows a schematic view a UAV having different flip heights andradii, in accordance with embodiments of the present disclosure.

FIG. 4 shows a schematic view of a UAV changing its orientation whileflipping from a landing surface to mid-air, in accordance withembodiments of the present disclosure.

FIG. 5 shows a schematic view of a UAV changing its orientation while inflight in response to a detected threshold condition, in accordance withembodiments of the present disclosure.

FIG. 6 shows a schematic view of a UAV changing its orientation duringflight, in accordance with embodiments of the present disclosure.

FIG. 7 shows a schematic view of a UAV changing its orientation whenflipping from an upward sloping surface to a horizontal landing surface,in accordance with embodiments of the present disclosure.

FIG. 8 shows a schematic view of a UAV changing its orientation whenflipping from an upward sloping surface to mid-air, in accordance withembodiments of the present disclosure.

FIG. 9 shows a schematic view of a UAV changing its orientation whenflipping from a downward sloping surface to a horizontal landingsurface, in accordance with embodiments of the present disclosure.

FIG. 10 shows a schematic view of a UAV changing its orientation whenflipping from a downward sloping surface to mid-air, in accordance withembodiments of the present disclosure.

FIG. 11 shows a schematic view of a UAV changing its orientation inresponse to a user command, in accordance with embodiments of thepresent disclosure.

FIG. 12 illustrates a schematic view of a flight control system of a UAVthat is capable of effecting a change in orientation of the UAV, inaccordance with embodiments of the present disclosure.

FIG. 13 illustrates a schematic view of the rotation directions ofpropulsion units of a UAV when the UAV is in different orientations, inaccordance with embodiments of the present disclosure.

FIG. 14 illustrates a schematic view of a UAV capable of flipping alonglines that are diagonal to a central body of the UAV, in accordance withembodiments of the present disclosure.

FIG. 15 illustrates a schematic view of a UAV capable of flipping aboutmultiple axes defined with respect to a central body of the UAV, inaccordance with embodiments of the present disclosure.

FIG. 16 provides an illustration of various components of a UAV, inaccordance with embodiments of the present disclosure.

FIG. 17 is a schematic block diagram of a system for controlling amovable object, in accordance with some embodiments.

DETAILED DESCRIPTION

Systems and methods are provided herein for enabling multi-orientationflight, take-off, and landing of an aerial vehicle. An aerial vehicle,such as an unmanned aerial vehicle (UAV), may support one or morepropulsion units that are configured to generate lift for the aerialvehicle. Any description herein of a UAV may apply to any type of aerialvehicle or UAV, or vice versa. The UAV may be capable of flight in afirst orientation and a second orientation different from the firstorientation. The second orientation can be an orientation that isopposite to the first orientation. For example, the UAV may be in aright-side up position when it is in the first orientation, and the UAVmay be in an upside-down position when it is the second orientation. TheUAV may be configured to take off, land, and/or fly around in the firstorientation and the second orientation. This may be particularly usefulin situations where the UAV may land or crash on a surface in anuncontrolled manner. In some cases, the UAV may land on a surface in anupside down orientation, right-side up orientation, or tiltedorientation. The UAV disclosed herein may be capable of re-launch intoflight from the surface, regardless of an orientation in which the UAVis landed on the surface.

The UAV may be capable of changing its orientation in differentscenarios. For instance, the UAV may change orientation while the UAV ison a landing surface. In some cases, the UAV may take off for flightafter changing its orientation. In another example, the UAV may take offfrom a landing surface, and then change orientation in mid-air (duringflight) in response to a detected threshold condition. In someinstances, the UAV may change orientation in response to a user command.This may occur when the UAV is on a landing surface, or in flight. Thismay allow the UAV to change orientations to accommodate varioussituations. Any combination of automated, semi-automated, or manualflight commands may be used to control the UAV to change orientations.This may advantageously permit novice users, as well as advanced users,to control the UAV to change flight orientations for various scenarios.

The change in UAV orientation may occur by controlling operation of oneor more propulsion units of the UAV. The propulsion units of the UAV mayinclude rotatable components (e.g., rotor blades), that may be capableof rotating in different directions and at different speeds. Forinstance, a propulsion unit may rotate in a first direction to generatelift for the UAV when the UAV is in a first orientation, and may rotatein a second direction opposite the first direction to generate lift forthe UAV when the UAV is in a second orientation. One or more electronicspeed control (ESC) units may be in communication with one or morepropulsion units to control operation of the propulsion units. Forinstance, an ESC control unit may control the direction and/or speed ofrotation of one or more rotor blades of a propulsion unit. Anydescription of a rotor blade elsewhere herein may also apply to a rotor,and vice versa.

Protective covers may be provided for the propulsion units of the UAV.The protective covers may protect rotatable components of the propulsionunits from external impact. For example, the protective covers mayprevent rotatable components of the propulsion units from contacting anunderlying surface when the UAV is landed on the underlying surface. Theprotective covers may be configured to surround the rotatable componentsof the propulsion units, and serve as an enclosure for the rotatablecomponents. Through use of the protective covers, the rotors of the UAVcan rotate freely even though the UAV may be landed upside down or onits side. This may be particularly advantageous for permitting acrash-landed UAV to take off from various orientations, since the UAVmay unpredictably land in various orientations or in different types ofenvironments.

FIG. 1 shows an exemplary embodiment of an unmanned aerial vehicle (UAV)capable of flight in multiple orientations, in accordance withembodiments of the present disclosure. The UAV may include a body 102configured to support one or more propulsion units 103. The propulsionunits may function to generate downward propulsion 120 therebygenerating a lift 118 or a thrust to the UAV.

Each propulsion unit 103 may include a set of rotating components. Eachset of rotating components may include one or more rotor blades 110 a,110 b capable of rotating in two directions. The two directions may beopposite to each other. For example, the first direction may be aclockwise direction, and the second direction may be a counter clockwisedirection. The one or more rotor blades 110 a, 110 b of the samerotating component or propulsion unit may be actuated by one or moreactuators or motors. One or more rotor blades 110 a, 110 b of the samepropulsion unit may be connected to a hub 128, and configured to rotateabout the hub. Each propulsion unit may also include a support structure108 for one or more of: rotor blade(s) 110 a, 110 b, the actuator(s),and optionally the hub. For instances, a propulsion unit may include tworotor blades actuated by the same motor.

The rotor blades may be configured to rotate in different directions togenerate lift for the UAV, or to change an orientation of the UAV. Forexample, the UAV may be configured to fly in a first orientation 100 awhen a first set of rotor blades are rotating in a first direction and asecond set of rotor blades are rotating in a second direction oppositeto the first direction. Conversely, the UAV may be configured to fly ina second orientation 100 b when the first set of rotor blades arerotating in the second direction and the second set of rotor blades arerotating in the first direction. The UAV may be capable of taking offand flying in either the first orientation 100 a or the secondorientation 100 b. After the UAV has taken off from a surface, the UAVmay be capable of changing its orientation in mid-air (e.g., duringflight) from the first orientation 100 a to the second orientation 100b. The change in orientation may be triggered by a pre-determinedcondition. In some cases, the change in orientation can be performedautonomously or semi-autonomously without user intervention.

In various embodiments, disclosed herein are UAVs including one or morepropulsion units (e.g., 4 propulsion units in FIG. 1) configured togenerate lift for the UAV. In some cases, the UAV may include 2, 4, 6,8, 10, 12, 14, or any other number of propulsion units. The one or morepropulsion units may include a first set of rotating components 110 a(along a first diagonal 124 of the UAV) and a second set of rotatingcomponents 110 b (along a second diagonal 126 of the UAV). The first setof rotating components (e.g. 1 or 3 in FIG. 15) may be configured torotate in a first direction and the second set of rotating components(e.g. 2 or 4 in FIG. 15) are configured to rotate in a second directionwhen the UAV is in a first orientation (100 a) and the first set ofrotating components are configured to rotate in the second direction andthe second set of rotating components are configured to rotate in thefirst direction when the UAV is in a second orientation (100 b) oppositethe first orientation. The first and second diagonals are within the x-yplane and are not parallel to the pitch axis (x axis) and roll axis (yaxis). The first or the second diagonal may be about 10 degrees to about80 degrees tilted from the pitch axis or the roll axis. In someinstances, the first and second directions may include a clockwisedirection and a counter clockwise direction. For example, the UAV may beupside down when it is in the first orientation, and right-side up whenit is in the second orientation.

In some cases, each propulsion unit is directly attached to the outersurface of the central body 102. Alternatively, each propulsion unit maybe attached to the central body through an arm extending from the outersurface of the central body. One end of the arm may attach to the outersurface of the central body via one or more joints. Another end of thearm may be configured to support the propulsion unit. The joints may fixthe arm to the central body, thus allowing the arm to move with thecentral body as an integral piece.

A protective cover 106 may be provided to protect each propulsion unitfrom impact or damage. The protective cover 106 can prevent thepropulsion unit and the components therein from contacting externalobjects or a surface. Each protective cover may have a top edge 114 anda bottom edge 112. The UAV may be either in a first orientation 100 a ora second orientation 100 b. The UAV may be configured to fly or hover ineither orientation (100 a or 100 b). The top edge may face upward in thesecond flight orientation while the bottom edge may face downward in thesecond orientation. The first and second orientation may be oppositefrom each other. The protective cover may be a separate component fromthe propulsion unit. In other embodiments, the protective cover may bepart of the propulsion unit. The protective cover may be releasablycoupled to the body of the UAV. Alternatively, the protective may beintegrally formed with the body of the UAV. For some instances, theprotective cover may be directly attached to the body of the UAV.

The UAV may include one or more protective covers 106 that prevent theone or more propulsion units from directly contacting an externalobject. In some cases, a height h_(pc) of the one or more protectivecovers 106 is greater than a height h_(b) of a body 102 of the UAV (FIG.17). In some cases, a height h_(pc) of the one or more protective coversis greater than a height of the one or more propulsion units (e.g.,height h_(rb) of rotors 110 a, 110 b, motors, and supporting structures108) (FIG. 17). In some cases, each of the one or more protective covers106 forms a tunnel around a corresponding propulsion unit of the one ormore propulsion units. The tunnel structure may surround the propulsionunit on its side, while exposing its top and bottom. This structure mayallow and/or facilitate the lift force 118 to be generated through andfrom the top and bottom of the tunnel structure. In some cases, eachprotective cover comprises a sleeve in which a propulsion unit isdisposed. The tunnel or sleeve of the protective cover may have adiameter (e.g. 704 in FIG. 7) that is sufficient to allow a set ofrotating components to be enclosed therein and rotates in bothdirections. In some cases, the one or more protective covers permit theone or more rotating components of the one or more propulsion units torotate in the first direction or the second direction when the UAV is onan underlying surface. The rotating component may include a rotor (orrotor blades), a set of rotor(s), and/or a motor actuating the rotor(s).

The UAV may include one or more one or more processors configured toindividually or collectively control direction and speed of the firstset of rotating components and the second set of rotating components ofthe one or more propulsion units. In some cases, the one or moreprocessors are located in one or more ESC units and/or a flightcontroller. In alternative embodiments, the one or more processors arelocated in the central body or remotely off the UAV. In some cases, theprocessors may be configured to generate a signal to control one or morepropulsion units. In some cases, a signal from the one or moreprocessors is configured to cause the UAV to change orientations betweenthe first orientation and the second orientation.

The UAV may include one or more sensors. Any sensor for collectingenvironmental information can be used, including location sensors (e.g.,global positioning system (GPS) sensors, mobile device transmittersenabling location triangulation), vision sensors (e.g., imaging devicescapable of detecting visible, infrared, or ultraviolet light, such ascameras), proximity sensors (e.g., ultrasonic sensors, lidar,time-of-flight cameras), inertial sensors (e.g., accelerometers,gyroscopes, inertial measurement units (IMUs)), altitude sensors,pressure sensors (e.g., barometers), audio sensors (e.g., microphones)or field sensors (e.g., magnetometers, electromagnetic sensors). Anynumber and combination of sensors can be used, such as one, two, three,four, five, or more sensors. Optionally, the data can be received fromsensors of different types (e.g., two, three, four, five, or moretypes). Sensors of different types may measure different types ofsignals or information (e.g., position, orientation, velocity,acceleration, proximity, pressure, etc.) and/or utilize different typesof measurement techniques to obtain data. For instance, the sensors mayinclude any combination of active sensors (e.g., sensors that generateand measure energy from their own source) and passive sensors (e.g.,sensors that detect available energy).

The sensor data may provide various types of environmental information.For example, the sensor data may be indicative of an environment type,such as an indoor environment, outdoor environment, low altitudeenvironment, high altitude environment, etc. The sensor data may alsoprovide information regarding current environmental conditions,including weather (e.g., clear, rainy, snowing), visibility conditions,wind speed, time of day, and so on. Furthermore, the environmentalinformation collected by the sensors may include information regardingthe objects in the environment, such as structures or obstacles.

In some embodiments, the one or more sensors can comprise one or moreof: a GPS sensor, an inertial sensor, a vision sensor, a lidar sensor,an ultrasonic sensor, a barometer, or an altimeter. The one or moresensors can comprise a plurality of different sensor types. The one ormore sensors can comprise a GPS sensor and the environment type can bedetermined based on a number of GPS satellites in communication with theGPS sensor. The one or more sensors can comprise a lidar sensor and theenvironment type can be determined based on time-of-flight data obtainedby the lidar sensor. The one or more sensors can comprise a visionsensor and the environment type can be determined based on image dataobtained by the vision sensor, such as an exposure time associated withthe image data obtained by the vision sensor.

In some embodiments, at least some of the sensors may be configured toprovide data regarding a state of the UAV. The state informationprovided by a sensor can include information regarding a spatialdisposition of the UAV (e.g., position information such as longitude,latitude, and/or altitude; orientation information such as roll, pitch,and/or yaw). The state information can also include informationregarding motion of the UAV (e.g., translational velocity, translationacceleration, angular velocity, angular acceleration, etc.). A sensorcan be configured, for instance, to determine a spatial dispositionand/or motion of the UAV with respect to up to six degrees of freedom(e.g., three degrees of freedom in position and/or translation, threedegrees of freedom in orientation and/or rotation). The stateinformation may be provided relative to a global reference frame orrelative to the reference frame of another entity. For example, a sensorcan be configured to determine the distance between the UAV and the userand/or the starting point of flight for the UAV.

The sensing data provided by the one or more sensors can be used tocontrol the spatial disposition, velocity, rotating direction of eachset of blades, rotating direction of one or more propulsion units,rotation speed of each set of rotor blades, and/or orientation of theUAV (e.g., using a digital signal processing device, a processor, and/orcontrol module). Alternatively, a sensor can be used to provide dataregarding the environment surrounding the UAV, such as weatherconditions, proximity to potential obstacles, location of geographicalfeatures, location of manmade structures, a wind speed, a winddirection, a rain speed, a temperature, and the like. Such environmentaldata may be with respect to up to three degrees of translation and up tothree degrees of rotation.

The UAV may include at least one communication device. The communicationdevice may enable communication with remote terminal(s) via wirelesssignal. The communication device may include any number of digitalprocessors, software modules, transmitters, receivers, and/ortransceivers for wireless communication. The communication may beone-way communication, such that data can be transmitted in only onedirection to or from the UAV. For example, one-way communication mayinvolve only the UAV transmitting data to the terminal, or vice-versa.The data may be transmitted from one or more transmitters of thecommunication devices to one or more receivers of the communicationsystem, or vice-versa. Alternatively, the communication may be two-waysuch that data can be transmitted in both directions between the UAV andthe terminal. The two-way communication can involve transmitting datafrom one or more transmitters of the communication system to one or morereceivers of the terminal, and vice-versa. The communication device maybe located at any part of the UAV; for example, in the body 102, theprotective cover 106, the rotors 110 a, 110 b, and/or the supportingstructure 108.

In some embodiments, the UAV may include a remote terminal. The terminalcan be a remote control device at a location distant from the UAV. Theterminal can be disposed on or affixed to a support platform.Alternatively, the terminal can be a handheld or wearable device. Insome cases, the terminal may include a smartphone, tablet, laptop,computer, glasses, gloves, helmet, microphone, or combinations thereof.The terminal can include a user interface, such as a keyboard, mouse,joystick, touchscreen, or display. Any user input can be used tointeract with the terminal, such as manually entered commands, voicecontrol, gesture control, or position control (e.g., via a movement,location or tilt of the terminal).

The terminal can be used to control any state of the UAV, carrier,and/or payload. For example, the terminal can be used to control theposition and/or orientation of the UAV, carrier, and/or payload relativeto a fixed reference from and/or to each other. In some embodiments, theterminal can be used to control individual elements of the UAV, carrier,and/or payload, such as one or more actuators, one or more propulsionunits, a sensor, a landing gear. The terminal can include a wirelesscommunication device adapted to communicate with one or more of the UAV,carrier, or payload, or individual elements within the UAV.

The terminal can include a display unit for viewing information of theUAV, carrier, and/or payload. For example, the terminal can beconfigured to display information of the UAV, carrier, and/or payloadwith respect to position, translational velocity, translationalacceleration, orientation, angular velocity, angular acceleration,angular momentum, battery remaining, rotor blades speed, rotatingfrequency of rotor blade(s), rotating direction of rotor blade(s),orientation of UAV, or any combinations thereof. In some embodiments,the terminal can display information provided by the payload, such asdata provided by a functional payload (for example, images recorded by acamera or other image capturing device).

Optionally, the same terminal may control the UAV, carrier, and/orpayload, or a state of UAV, carrier and/or payload, as well as receiveand/or display information from the UAV, carrier and/or payload. Forexample, a terminal may control the orientation of the UAV relative toan environment, while displaying data captured by one or more sensors,or information about the position of the UAV. Alternatively, differentterminals may be used for different functions. For example, a firstterminal may control movement or a state of the UAV, carrier, and/orpayload while a second terminal may receive and/or display informationfrom the UAV, carrier, and/or payload. For example, a first terminal maybe used to control the orientation of the UAV relative to an environmentwhile a second terminal displays data captured by one or more sensors.Various communication modes may be utilized between an UAV and anintegrated terminal that both controls the UAV and receives data, orbetween the UAV and multiple terminals that both control the UAV andreceives data. For example, at least two different communication modesmay be formed between the UAV and the terminal that both controls theUAV and receives data from the UAV.

The UAV may have at least a first flight orientation 100 a, and a secondflight orientation 100 b. The first flight orientation and the secondflight orientation may be opposite to each other. In some cases, thefirst orientation is for the UAV to be upside down. In some cases, thesecond orientation is for the UAV to be right-side up. In some cases,the UAV is capable of taking off from an underlying surface in the firstorientation and in the second orientation. In some cases, the UAV iscapable of hovering or flight when in the first orientation and in thesecond orientation. The first flight orientation and the second flightorientation may be about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110,120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250,260, 260, 270, 280, 290, 300, 310, 320, 330, 340, or 350 degrees indifference. For example, in the right-side up flight orientation, afirst portion 114 (for example, a top edge) of the protective cover maybe substantially facing upward and may be farther to the ground than asecond portion 116 (for example, a bottom edge) of the protective cover.Conversely, in the upside down flight orientation, the first portion(for example, the top edge) of the protective cover may be substantiallyfacing downward and may be closer to the ground than the second portion(for example, bottom edge) of the protective cover.

As another example, in the right side up flight orientation, topsurface(s) 130 of the rotor blades 110 a, 110 b may be substantiallyfacing upward and may be farther to the ground than the bottomsurface(s) 132 of the rotor blades. Conversely, in the upside downflight orientation, the top surfaces(s) of the rotor blades may besubstantially facing downward and may be closer to the ground than thebottom surface(s) of the rotor blades. In some embodiments, one of thefirst and the second orientations may be a common or more frequentlyused flight orientation of the UAV, while the other one of the first andthe second orientations may be a less common or less frequently usedflight orientation of the UAV. For example, the second orientation (inwhich the UAV is right-side up) may be more commonly used, while thefirst orientation (in which the UAV is upside down) may be less commonlyused. In some cases, when the UAV first takes off, the first portion ofthe protective cover of the UAV may face upward and the second portionof the protective cover may face downward. In other cases, when the UAVfirst takes off, the first portion of the protective cover of the UAVmay face downward and the second portion of the protective cover mayface upward.

In some embodiments, the first flight orientation 100 a and the secondflight orientation 100 b may be not substantially parallel to eachother. When the first orientation and the second orientation aresubstantially opposite to each other with about 180 degrees indifference, they may not be substantially parallel to each other. Thefirst flight orientation and the second flight orientation may have anyangle of difference in the range from 1 degree to about 359 degrees. Thefirst flight orientation and the second flight orientation may be atleast about 30, 45, 60, 90, 120, 135, 150, 180, 210 degrees and so forthdifferent from each other (e.g. FIGS. 6-10). As an example, in the firstflight orientation, the UAV may be parallel to a horizontal (x-y planein FIG. 1) plane and may have the top surface(s) of the rotor bladesfacing upwards and the bottom surfaces facing downwards. In the secondflight orientation, the UAV may be 30 degrees tilted from the horizontalplane, with the right-side of the UAV higher than the left-side of theUAV relative to a horizontal plane, and the front-side and rear-side ofthe UAV are at the same height (e.g., FIG. 6). Alternatively, in a rightside up orientation, each of the propulsion units of the UAV can have adifferent height to an external object (e.g. a ground, a water surface)as shown in FIG. 18. In this embodiment, the pitch, roll, and/or yawaxis of the UAV may be oblique to the horizontal plane or the liftdirection.

The UAV may have any number of possible flight orientations. Each twoflight orientations among the possible orientations may not besubstantially identical to each other. Each two flight orientationsamong the possible orientations may not be substantially parallel toeach other. When the first orientation 100 a and the second orientation100 b are substantially opposite to each other with about 180 degrees indifference, the UAV in two different flight orientations may looksimilar after the UAV has changed its orientation. The UAV can changeits orientation, for example by rotating about its plane of symmetryfrom one orientation to another orientation. The UAV may have asymmetrical axis extending from its front-side to its rear-side alongthe roll axis (y axis in FIG. 1). In other words, the UAV may besymmetric from left to right along the pitch axis (x axis in FIG. 1).Alternatively, two different flight orientations may look similar toeach other when the UAV has a symmetrical axis extending from itsleft-side to its right-side along the pitch axis (x axis in FIG. 1). Inother words, the UAV may be symmetric from front to rear along the rollaxis (y axis in FIG. 1). Two different flight orientations may looksimilar to each other when the UAV has a symmetrical axis running fromits top to its bottom along the yaw axis (z axis in FIG. 1). As anexample, the UAV with the right-side up may look similar as the UAV withits upside down.

The protective covers may be in a shape that is symmetric from its topedges to bottom edges along the yaw axis (z axis in FIG. 1). When viewedfrom above the UAV, the rotator blades may rotate in the same clockwiseor counter clockwise direction when the UAV is upside down.Alternatively, the rotator blades may rotate in an opposite rotatingdirection when the UAV is upside down. The central body may be symmetricabout a horizontal plane (x-y plane in FIG. 1). A first distance of therotor blades to the top edge of the protective cover may besubstantially the same as a second distance of the rotor blades to thebottom edge of the protective cover. Alternatively, the first distanceand the second distance may be substantially different. In some cases,the first distance may be greater than the second distance.Alternatively, the first distance may be less than the second distance.In some cases, the UAV has at least one, two, or three planes ofsymmetry. The plane(s) may be orthogonal to each other when there aretwo or more planes of symmetry. The plane(s) may be oblique to eachother. As an example, a plane of symmetry of the UAV may be parallel tothe horizontal plane (x-y plane in FIG. 1), or the top and bottomsurfaces of the central body, and located at middle point of the heightof the central body. As another example, a plane of symmetry of the UAVmay be parallel to the right or left surfaces of the central body andlocated at the mid-point of the width of the central body. In otherwords, a plane of symmetry of the UAV may be parallel to y-z plane orx-z plane in FIG. 1. As another example, a plane of symmetry of the UAVmay be orthogonal to the right or left surfaces of the central body andlocated at the mid-point of the length of the central body. In somecases, the plane of symmetry may virtually separate the UAV into twoparts with identical numbers of same type of elements (for example,propulsion units, rotor blades, arms, motors). In some cases, the planeof symmetry may virtually separate the UAV and one or more elementstherewithin in halves. As an example, a plane of symmetry from theright-front tip of the UAV to the left-rear tip of the UAV may separatetwo propulsion units into four halves.

In some embodiments, a UAV (or one or more of its components) may beasymmetric in shape, weight, or density around a rotational axis of theUAV. In those embodiments, the UAV in two different flight orientationsmay look different when the UAV changes from a first orientation to asecond orientation. As an example, the UAV may look different when it isupside down compared to when the UAV is right side up. The protectivecovers may have a shape that is asymmetric from its top edges to bottomedges (about a horizontal plane). The rotator blades may or may notrotate in the same clockwise or counter clockwise direction when the UAVis upside down. The central body may be asymmetric from its top surfacesto bottom surfaces (about a horizontal plane). The rotor blades may havedifferent distances to the top and the bottom edges of the protectivecovers. The UAV may include a structural shape that only exists at thebottom surface or top surface of the protective cover. The UAV mayinclude a landing gear that only exists at the bottom side of the UAV.The UAV may use different materials at its bottom and its top side. TheUAV may have a central body shape that is a symmetric about a plane ofrotation, the plane of rotation may be any three dimensional plane.

The UAV may sense its orientation, or a change of orientation using oneor more sensing units. The sensing unit may be a sensor as disclosedherein. The sensing unit may be any number of sensors. The sensing unitmay be located on the UAV or off-board of the UAV. The sensing unit maybe located at any part of the UAV, for example, in the body 102, theprotective cover 106, the rotors 110 a, 110 b, and/or the supportingstructure 108. In some cases, the sensing unit is a combination of anynumber of sensors on the UAV and any number sensors off from the UAV.

Any sensor for collecting environmental information can be used,including location sensors (e.g., global positioning system (GPS)sensors, mobile device transmitters enabling location triangulation),vision sensors (e.g., imaging devices capable of detecting visible,infrared, or ultraviolet light, such as cameras), proximity sensors(e.g., ultrasonic sensors, lidar, time-of-flight cameras), inertialsensors (e.g., accelerometers, gyroscopes, inertial measurement units(IMUs)), altitude sensors, pressure sensors (e.g., barometers), audiosensors (e.g., microphones) or field sensors (e.g., magnetometers,electromagnetic sensors). Any number and combination of sensors can beused, such as one, two, three, four, five, or more sensors. Optionally,the data can be received from sensors of different types (e.g., two,three, four, five, or more types). Sensors of different types maymeasure different types of signals or information (e.g., position,orientation, velocity, acceleration, proximity, pressure, etc.) and/orutilize different types of measurement techniques to obtain data. Forinstance, the sensors may include any combination of active sensors(e.g., sensors that generate and measure energy from their own source)and passive sensors (e.g., sensors that detect available energy).

The sensors may directly sense data selected from: position, positionchange at two time points, translational velocity, translationalvelocity change at two time points, translational acceleration, changein translational acceleration at two time points, orientation, angularvelocity, change in angular velocity at two time points, angularmomentum, change in angular momentum at two time points, angularacceleration, change in angular acceleration at two time points, rotorblades speed, rotor blades frequency, rotating direction of rotorblade(s) or any combinations thereof with respect to up to three degreesof translation and up to three degrees of rotation. The sensors maysense data that may be used to derive or generate information regardingthe above-listed data. Data sensed by and collected from the sensors areoptionally processed so that they may be analyzed at a certainconfidence level. The processed or unprocessed raw data from one or moresensors may be analyzed to yield orientation of the UAV.

The UAVs and methods of operating an UAV as disclosed herein may includegenerating a signal that causes the UAV to flip from a first orientationto a second orientation opposite the first orientation via one or moreprocessors from the flight controller or the electrical signal controlunit (ESC). Further, the UAVs and methods of operating the UAV asdisclosed herein may include effecting the flip of the UAV from thefirst orientation to the second orientation in response to the signalwith aid of one or more propulsion units. The UAV may change orientation(e.g., flip) via control of rotational speed and/or direction of one ormore propulsion units. The UAV may change orientation via control ofrotational speed and/or direction of one or more rotor blades. As anexample, an UAV with four propulsion units may include two pairs ofidentical fixed pitched rotors; two rotating clockwise on a diagonal andtwo rotating counter-clockwise on the other diagonal of the UAV in oneflight orientation. To change to another orientation, the rotationalspeed or orientation of one pair of rotors may change with or withoutthe change of speed or orientation of the other pair of rotors. Asanother example, when an obstacle is detected to the left side of theUAV, the UAV may increase the rotational speed of two propulsion unitson the left-side of the UAV so that the left side may be lifted furtherup along a vertical direction than the right side to avoid the obstacle.As another example, when the UAV hits an obstacle and flippedaccidentally, the UAV may automatically revert the rotation direction ofall propulsion units to resume flying with the flipped orientation andlater increase the rotational speed of one or more propulsion units(e.g. two propulsion units on the right-side of the UAV) optionally withdecrease of other propulsion units (e.g. two propulsion units on theleft-side of the UAV) so that the right side of the UAV may be lifted upand the left side may be lowered to produce a 90 degree rotation andeventually 180-degree flip of the entire UAV about the roll axis of theUAV. The rotational speed and direction of each propulsion unit may beindividually adjusted during the flip and/or after the UAV is flipped.

With control of each propulsion unit separately or together, theflipping type, and the flipping velocity of the UAV may be controlled.The flipping velocity may have a constant magnitude with a varyingdirection. The flipping velocity may be varying in both its magnitudeand direction. The magnitude of flipping velocity may include any shapeof waveform that starts from zero at the onset of flipping and ends atzero at the end of flipping.

The UAV may rotate and flip about the roll axis (y axis in FIG. 1). TheUAV may flip about the pitch axis (x axis in FIG. 1). The UAV may rotateabout the yaw axis (z axis in FIG. 1). The flip angle may be any anglegreater than about 1 degree to the initial orientation before the flip.The flip angle may be 15, 30, 45, 60, 75, 90, 105, 120, 135, 1550, 165,180, 195, 210, 225, 240, 255, 270, 285, 300, 315, 330, 345, 360 degreesor any other angles greater than 1 degree and less than 360 degrees.Alternatively, the flip angle may be greater than 360 degrees when theUAV may flip more than one revolution from the first orientation to thesecond orientation. As an example, the UAV flips from left to right for180 degrees from its initial orientation in a horizontal plane, so thatthe UAV is upside down and its left-side is flipped to the right. Asanother example, the UAV flips from rear to front for 90 degrees fromits initial orientation in a horizontal plane, so that the UAV isrear-side up and its front side is flipped to the bottom.

In a flip or a change of orientation of the UAV, the UAV may havehorizontal movement (in an x-y plane in FIG. 1), vertical movement(along z axis in FIG. 1), rotational movement (about a flipping axise.g., FIGS. 13-15), or a combination thereof. A flip or change oforientation may occur when the UAV hovers, moves, maintains a sameposition, lands, touches an external object, fails to move in a certaindirection, detects error in at least one UAV elements, or malfunctionsin an orientation.

The flip or change of orientation of the UAV may occur with or withoutthe assistance from one or more sensors. The UAV may change itsorientation when a signal is given from its control unit or terminal. Infurther cases, the control unit or terminal may control speed of flip,rotational angle of the flip, type of flip (e.g. left to right, front torear), or other aspects of the flip. As an example, when an obstacle isdetected to the left side of the UAV by a sensor, the UAV may increasethe rotational speed of one or two propulsion units on the left-side ofthe UAV so that the left side may be lifted further up than the rightside to avoid the obstacle. As another example, a UAV moves toward atree branch and touches it within a user's eyesight; the user may entera flip signal using a remote control with a selected flip angle, aselected flipping axis (e.g., FIG. 13-15), and/or a radius of the arcdefining flipping path. The selected flip angle may be, for example, 25degrees, 30 degrees, 45 degrees, or any angle. The flip angle may be anyangle that allows the UAV to safely avoid the obstacle. The flippingaxis may be parallel to the roll axis. Any value of the radius of thearc may be contemplated. In some cases, the radius may be about 10meters. The UAV may flip the selected flip angle about the selectedflipping axis from its initial orientation to be right-side up (tiltedfrom a vertical plane), thus it moves away from the tree branch.

FIG. 2 shows a schematic view of a UAV changing its orientation on ahorizontal landing surface, in accordance with embodiments of thepresent disclosure.

The UAV and elements therewithin may include a first orientation 200 aand a second orientation 200 b. When the UAV contacts an underlyingsurface or a landing surface 206 with its bottom portion 202 facingdownward and its top portion 204 facing upward, the UAV may be in thesecond orientation 200 b. Conversely, when the UAV is in the firstorientation, the top portion 204 may be facing downward and the bottomportion 202 of the UAV may be facing upward. The UAV may change itsorientation from 200a to 200 b, or vice versa when it is on a landingsurface. The first orientation and the second orientation may beopposite to each other with about a 180 degree difference. The UAV maybe configured to perform a flip 212 from the first orientation to thesecond orientation at a certain time point t₁, or vice versa. The UAVmay have an intermediate flight orientation 200 c while it flips fromthe first to the second orientation, or vice versa. The UAV may takeoffafter the flip at a certain time point t2.

The UAV disclosed herein may be flipped from the first orientation 200 ato the second orientation 200 b opposite the first orientation while theUAV is on an underlying surface 206. Before initiation of the flip, theUAV may obtain data indicative of a user input to initiate the flip ofthe UAV from the first orientation to the second orientation. The userinput may be received at a terminal remote to the UAV via a wirelessconnection. Alternatively, the UAV may obtain data from one or moresensors on-board the UAV to initiate the flip of the UAV from the firstorientation 200 a to the second orientation 200 b. The one or moresensors may detect an orientation of the UAV. The first orientation ofthe UAV may be upside down while the second orientation of the UAV maybe right side up. The UAV may be on the underlying surface for at leasta moment in time after flipping to the second orientation. This may beadvantageous to allow time for the UAV to check the functions of one ormore of its components. Additionally, this may be advantageous for theUAV to detect and/or change the rotational speed or orientation of oneor more rotating components to ensure safe flight. The time period(moment in time) may be about 0.1 second to about 100 seconds. The UAVmay effect, with aid of the one or more propulsion units, takeoff of theUAV from the underlying surface subsequent to the flip of the UAV fromthe first orientation to the second orientation. The UAV may furthereffect flight of the UAV in the second orientation optionally after theflip.

The landing surface 206 may be any static or moving surface that isconfigurable to hold at least part of the weight of the UAV. The landingsurface may be of different terrain. The landing surface may be flat,inclined (e.g., angle of inclination may be 5 degrees, 10 degrees, 15degrees, 20 degrees, 25 degrees, 30 degrees, and so forth), declined,even, uneven, or at any angle to the horizontal plane. For example, thelanding surface may be a roof, a tree branch, a ground, a floatingobject in the water, a water surface, a foliage covered surface, a rocksurface, a grass-land, a swamp surface, an aircraft, a sand surface, orthe like. The landing surface may be close or far from the user, theremote control, and/or the terminal. The landing surface may be in theuser's eyesight or within the control range of the remote control and/orthe terminal. The landing surface may be outside of the user's eyesightor outside of the control range of the remote control and/or theterminal.

The UAV may be on the landing surface 206 in the first orientation 200a, the second orientation 200 b, or any other orientation it may have.The UAV may be placed on the landing surface for a new take off.Alternatively, the UAV may be controlled to land on the landing surface,or may be land on the landing surface unintentionally after a crashlanding caused by external sources or internal malfunction of one ormore of the elements.

The UAV may automatically detect its orientation on the landing surfacewith the assistance of one or more sensors. Each of the one or moresensors may sense one or more properties of the UAV or the environmentsurrounding the UAV. Such a property may include one or more propertiesat one or more physical locations of the UAV, selected from: a flightorientation, a spatial disposition, a velocity, an altitude, latitude,acceleration, a speed, a tilt angle, a height, a distance to an externalsubject. Such properties may be with respect to up to three degrees oftranslation and up to three degrees of rotation. Alternatively, the oneor more sensors can be used to provide data regarding the environmentsurrounding the UAV, such as weather conditions, proximity to potentialobstacles, location of geographical features, location of manmadestructures, a wind speed, a wind direction, a rain speed, a temperature,and the like. Such environmental data are with respect to up to threedegrees of translation and up to three degrees of rotation. Any sensorfor collecting environmental information can be used, including locationsensors (e.g., global positioning system (GPS) sensors, mobile devicetransmitters enabling location triangulation), vision sensors (e.g.,imaging devices capable of detecting visible, infrared, or ultravioletlight, such as cameras), proximity sensors (e.g., ultrasonic sensors,lidar, time-of-flight cameras), inertial sensors (e.g., accelerometers,gyroscopes, inertial measurement units (IMUs)), altitude sensors,pressure sensors (e.g., barometers), audio sensors (e.g., microphones)or field sensors (e.g., magnetometers, electromagnetic sensors). Anynumber and combination of sensors can be used, such as one, two, three,four, five, or more sensors. Optionally, the data can be received fromsensors of different types (e.g., two, three, four, five, or moretypes). Sensors of different types may measure different types ofsignals or information (e.g., position, orientation, velocity,acceleration, proximity, pressure, etc.) and/or utilize different typesof measurement techniques to obtain data. For instance, the sensors mayinclude any combination of active sensors (e.g., sensors that generateand measure energy from their own source) and passive sensors (e.g.,sensors that detect available energy).

For example, the one or more sensors may be configured to sense therelative position of the bottom portion 202 to the top portion 204, anddetermine the orientation using a pre-defined database correlatingpositions of bottom and top portions to different orientations. As anexample, inertial sensor like IMUs may detect the rotational movement ofthe UAV and by adding the rotational movement of the UAV to its initialorientation at its take off, the relative position of the bottom portionto the top portion may be determined. As another example, differentproximity sensors may be used at the bottom and top portions of the UAV,thus, the height difference of the bottom and top portion to an externalreference (e.g. a water surface, a roof) may be determined.

The UAV may determine if a flip or change of orientation is necessary ornot based on its current orientation and the landing surface and mayprovide a signal to the one or more rotors. In some cases, disclosedherein are methods of operating an UAV. The method may include providinga signal optionally from a flight control unit, an electrical signalcontrol unit, or the like on-board the UAV to one or more correspondingpropulsion units, thereby controlling directions of rotation of a firstset of rotating components and a second set of rotating components ofthe one or more propulsion units. In some cases, the first set ofrotating components may be configured to rotate in a first direction andthe second set of rotating components are configured to rotate in asecond direction when the UAV is in a first orientation. Conversely, thefirst set of rotating components may be configured to rotate in thesecond direction and the second set of rotating components areconfigured to rotate in the first direction when the UAV is in a secondorientation opposite the first orientation. The UAV may automaticallygenerate the signal to effect a flip when a current orientation of theUAV does not permit it to start or resume flying within a predeterminedperiod of time after it lands on the landing surface. The predeterminedperiod time may be about 0.1 second to about 10 minutes. The UAV mayalso generate the signal if the landing surface obstructs it from flyingor changing position. The one or more processors onboard or remote fromthe UAV may be configured to generate a signal to effect a flip tochange orientation if the landing surface is in its route. The one ormore processors onboard or remote from the UAV may be configured togenerate a signal to effect a flip to change orientation when it crashlanded on the landing surface and unintentionally flipped. The UAV mayautomatically determine if a flip or change of orientation is necessaryor not based on its current orientation and the landing surface.Alternatively, a user may provide an input to the remote controllerand/or terminal, to generate a signal for effecting a flip to change theorientation of the UAV. In other cases, a signal may be providedoptionally from a remote control and/or terminal to one or morecorresponding propulsion units, thereby controlling directions ofrotation of a first set of rotating components and a second set ofrotating components of the one or more propulsion units.

In some cases, the UAV may or may not be within a user's eyesight. As anexample, a UAV may have crash landed onto a roof top and flipped 180degrees from its initial orientation. The roof top may not within theuser's view. In some instances, if the UAV cannot or does not resumeflying from the roof top in a predetermined time period (e.g., within 10seconds after the crash), the UAV may be configured to automaticallyinitiate a flip of 180 degrees to revert to its initial orientation sothat it can fly off from the roof top and resume flight. This automaticdetermination and completion of a flip may not require user control orintervention, and allows the UAV to be restored quickly back to flight.As another example, a UAV may fly near a tree and may be obstructed bytree branches/leaves. The UAV may be configured to detect surrounding“landing surfaces” and flip or rotate to an orientation which allowsmovement of the UAV along a route with fewer or no obstacles.

The UAV may flip or change orientation on the landing surface 206. Theflip or change of orientation may include moving the UAV away from thelanding surface in a rotating motion. The UAV may experience differentrotation angle, angular velocity, angular momentum, differentacceleration, force, resistance, or the like during the flip. The flipor change of orientation may include moving the UAV to land on thelanding surface again after the rotating motion in the secondorientation.

The flip may be controlled or effected without damage caused to the UAVby the landing surface or by the rotating motion. The flip may becontrolled or effected based on the weight, size, shape of the UAV,and/or speed of the propulsion units so that the flip does not causedamage to the UAV or its components.

In some cases, the flip of the UAV may be about the roll axis, the pitchaxis, the yaw axis, or any axis within an x-y plane, x-z plane, or y-zplane (axes and planes as shown in FIG. 1). With control of one or morerotor blades separately or together, the flip of the UAV may becontrolled or effected. In particular, the control of one or more rotorblades 110 a, 110 b in FIG. 1 may include the rotating speed of one ormore rotor blades and the direction of rotation of one or more rotorblades. For example, a UAV with four propulsion units may flip due to acrash and land on a surface in a first orientation 200 a. When the UAVis in the first orientation, a first portion of the UAV 204 may betouching the landing surface 206 while a second portion 202 of the UAVmay be facing the opposite direction. Two sets of rotor blades ofpropulsion units on the left side of the UAV may be controlled to rotateat a first speed, and the rotor blades of propulsion units on the rightside of the UAV may be controlled to rotate at a second speed. The firstand second speeds may be controlled so that the UAV can rotate about theroll axis (y axis in FIG. 1) to be left-side up, and the UAV maycontinue rotating and flip about 180 degrees. The UAV may be configuredto rotate about the roll axis and flip at a substantially angular speed.Alternatively, the UAV may be configured to rotate about the roll axisand flip at variable angular speeds. During the flip, the rotor bladeson a diagonal of the UAV (e.g., 124 in FIG. 1) may be rotating in afirst direction, while rotor blades on the other diagonal (e.g. 126 inFIG. 1) may be rotating in an opposite direction from the firstdirection. After the flip, the second portion 202 may be touching thelanding surface 206 while the first portion 204 may be facing upward. Inthis orientation, the UAV may take-of and resume flying properly.Alternatively, to initiate the flip, the left set of rotors along thediagonal 126 of the UAV may increase rotational speed to an extent suchthat the left portion of the UAV closest to the set of rotors view formthe top moves up and later may cause flip of the entire UAV.

In some cases, the first portion 204 of the UAV is in contact with anunderlying surface 206 when the UAV is in the first orientation 200 a,and the second portion 202 of the UAV is in contact with the underlyingsurface when the UAV is in the second orientation 200 b. In some cases,the first and second portions are laterally (e.g., along z axis inFIG. 1) opposite to each other relative to a horizontal plane (e.g.,parallel to x-y plane in FIG. 1) passing through a body of the UAV. Insome cases, the second portion 202 is located above the body in adirection of lift generated by the one or more propulsion units when theUAV is in the first orientation 200 a. In some cases, the first portion204 is located above the body in a direction of lift generated by theone or more propulsion units when the UAV is in the second orientation200 b. In some cases, the first orientation is for the UAV to be upsidedown. In some cases, the second orientation is for the UAV to beright-side up. In some cases, the UAV is capable of taking off from anunderlying surface in the first orientation and in the secondorientation. In some cases, the UAV is capable of hovering or flightwhen in the first orientation and in the second orientation.

The UAV may take-off after a flip or change of orientation. The UAV mayfly away from the landing surface 206 after a flip or change oforientation. Alternatively, the UAV may hover above the landing surfaceafter a flip. The UAV may fly with in any direction and/or along anymotion path defined within a 3-dimensional space. The UAV may be capableof motion in six degrees of freedom.

The UAV may be configured to include an intermediate flight orientation200 c. The intermediate flight orientation may exist during a flip orchange of orientation of the UAV from an orientation (e.g., 200 a) to adifferent orientation (e.g., 200 b). The UAV may be in the intermediateflight orientation for any time between 0.001 second to about 10minutes. In the intermediate flight orientation, the UAV may be in theair. Alternatively, some portion of the UAV may be touching theunderlying surface 206. The intermediate flight orientation may haveabout half of the difference in angle between before and after fliporientations (e.g. the first and second flight orientations). As anexample, when the UAV flips about 180 degrees from the first to thesecond orientation, the intermediate orientation may have about 90degrees to the first and the second flight orientation. The intermediateflight orientation may have about 10, 20, 30, 40, 50, 60, 70, 80, 90,100, 110, 120, 130, 140, 150, 160, 170, 180, or any other number ofdegrees in difference to the first or the second flight orientation. TheUAV may stay in the intermediate flight orientation for about 0.01second to about 1000 seconds during its flip.

FIG. 3 shows a schematic view a UAV having different flip heights andradii, in accordance with embodiments of the present disclosure.

The embodiment in FIG. 3 may be similar to the embodiment in FIG. 2except for the following differences. In FIG. 3, a UAV may be configuredto adjust a flip or change of orientation while the UAV is on the groundsuch that the intermediate flight orientation 312 has different heights(e.g., h1 and h2) along a vertical direction. Similarly, the radius r ofan arc defining the flip motion path of the UAV 312 may be differentwith different heights. Additionally, a UAV may be configured to adjusta flip or change of orientation such that the UAV after the change oforientation may land in locations at difference distances (e.g., d1 andd2) to the UAV before the flip. The UAV may be configured to effect suchdifferences in the change of orientation with control of the rotationalspeeds and directions of one or more propulsion units therebycontrolling the flipping speed, flipping acceleration, flipping height(e.g., h1 and h2), flipping distance (e.g., d1 and d2), flipping radius,flipping axis (FIGS. 13-15), and/or other parameters of the UAV. Aradius of arc r (defining the UAV's motion path during the flip 312) mayrange from about 0 meter to about 0.3 meters. The flipping distance mayrange from about 0 meter to about 0.3 meters. The flipping height mayrange from about 0.2 meters to about 1 meter.

Such differences in change of orientation may be advantageous for theUAV to avoid external obstacles and ensure the success in change oforientation. As an example, the UAV may flip to a high enoughintermediate orientation and then to a different flight orientation suchthat a bump on the underlying surface may be avoided. As anotherexample, the UAV may flip to a location with a distance less than 0.01meter to the UAV before the flip to avoid flipping and landing in watersurface that is 0.03 m away and surrounding the UAV before the flip.

FIG. 4 shows a schematic view of a UAV changing its orientation whileflipping from a landing surface to mid-air, in accordance withembodiments of the present disclosure.

The embodiment in FIG. 4 may be similar to the embodiment in FIG. 2except for the following differences. In FIG. 4, The UAV on theunderlying surface may change orientation 412. During the change oforientation, the UAV may include an intermediate flight orientation 400c that is less than 90 degrees different from the first orientation 400a and more than 90 degrees from the second flight orientation 400 b. Atthe second orientation after the flip, the UAV may be above theunderlying surface with a height h_(ab). The UAV may resume flying inthe second flight orientation.

A radius of an arc (defining the UAV's motion path during the flip 412may range from about 0.2 meters to about 0.5 meters. The height h_(ab)may range from about 0.2 meters to about 0.5 meters above an underlyingsurface.

Such a flip 412 ending in a flight orientation in the air may beadvantages to avoid external obstacles that may exist on the underlyingsurface if the UAV were to land on the underlying surface and/orobstructions that may exist on other flip motion path(s) the UAV maytake. Additionally, such a flip may also ensure fast and efficientflight after the flip. As an example, the UAV may be configured tochange orientation with a flip 412 to avoid underlying surfacesurrounding the UAV that is not appropriate for a flipped UAV to landon.

FIG. 5 shows a schematic view of a condition under which the UAV maychange orientation while in flight in response to a detected thresholdcondition, in accordance with embodiments of the present disclosure.

The UAV may be disposed in one or more orientations. In someembodiments, the orientations may include a first orientation 500 a anda second orientation 500 b. In some instances, after a crash landing,the UAV may be in the first orientation 500 a in contact with anunderlying surface or a landing surface 506, such that its secondportion 504 is facing downward and its first portion 502 is facingupward relative to the underlying surface. The UAV may take off from thelanding surface 506 in the first orientation. In some embodiments, whenthe UAV meets a threshold condition (e.g., a height threshold 508), theUAV may change its orientation from 500 a to 500 b. The UAV may thenresume flying in the second orientation 500 b, with the second portion504 facing upward and the first portion 502 of the UAV facing downward.The first orientation and the second orientation may be parallel butlaterally opposite to each other (e.g., about 180 degrees difference).

In some cases, the first portion 504 (e.g., top portion) of the one ormore protective covers may be in contact with an underlying surface 506when the UAV is in the first orientation 500 a, and a second portion 502(e.g., bottom portion) of the one or more protective covers may be incontact with the underlying surface when the UAV is in the secondorientation 500 b. In some cases, the first and second portions of theone or more protective covers may be laterally opposite to each other(e.g., along the z-axis in FIG. 1) relative to a horizontal plane (e.g.,parallel to the x-y plane in FIG. 1) passing through a body of the UAV.In some cases, the second portion 502 may be located above the body in adirection of lift generated by the one or more propulsion units when theUAV is in the first orientation 500 a. In some cases, the first portion504 may be located above the body in a direction of lift generated bythe one or more propulsion units when the UAV is in the secondorientation 500 b.

The UAV may flip from the first orientation 500 a to the secondorientation 500 b opposite the first orientation when one or moresensors detect that the UAV has reached a threshold condition 508. Theone or more sensors may be onboard the UAV and may be configured todetect whether the UAV has reached the threshold condition when the UAVis in flight. The threshold condition may be reached during flight ofthe UAV. As an example, the threshold condition may be an altitude ofthe UAV with respect to the underlying surface. Alternatively, thethreshold condition may be a velocity or acceleration of the UAV withrespect to the underlying surface, wherein the velocity or accelerationis a vertical velocity or acceleration of the UAV with respect to theunderlying surface. Alternatively, the threshold condition may be powerprovided to the one or more propulsion units, or power consumed by theone or more propulsion units, an amount of time that has elapsed sincethe UAV has taken off from the underlying surface, or other conditions.Such power threshold condition may be used to prevent the rotor blades,motors, or other elements of the UAV. As an example, when one or morepropulsion units reaches over 90% of the maximal power allowed in theUAV without effecting the desired motion in the UAV (e.g., when the UAVis trapped by an external obstacle), the power threshold is satisfied.The UAV may be configured to effect a change of orientation that maymove the UAV away from the obstacle and resume proper operations. Insome case, the one or more propulsion units permit the UAV to take offfrom the underlying surface regardless of orientation of the underlyingsurface relative to the direction of gravity, wherein the firstorientation is for the UAV to be upside down and wherein the secondorientation is for the UAV to be right side up. The UAV comprises one ormore protective covers that prevent the one or more propulsion unitsfrom directly contacting the underlying surface. The underlying surfacemay be horizontal, included from the horizontal surface, declined fromthe horizontal surface, or a combination thereof.

The UAV may be on a landing surface 506 before it takes off, resumesflying, flip, or change its orientation. The landing surface may be anystatic or moving surface that is configurable to hold at least part ofthe weight of the UAV. The landing surface may be of different terrain.The landing surface may be flat, inclined, declined, even, uneven, or atany angle to the horizontal plane. For example, the landing surface maybe a roof, a tree branch, a ground, a floating object in the water, awater surface, a foliage covered surface, a rock surface, a grass-land,a swamp surface, an aircraft, a sand surface, or the like. The landingsurface may be close or far from the user, the remote control, and/orthe terminal. The landing surface may be in the user's eyesight orwithin the control range of the remote control and/or the terminal. Thelanding surface may be outside of the user's eyesight or outside of thecontrol range of the remote control and/or the terminal.

The UAV may be on the landing surface 506 in the first orientation 500a, the second orientation 500 b, or any other orientation it may have.The UAV may be placed on the landing surface 506 for a new take off.Alternatively, the UAV may be controlled to land on the landing surface,or may land on the landing surface unintentionally after a crash landingcaused by external sources or internal malfunction of one or more of theelements. In some cases, the landing surface and the surroundingenvironment may not be suitable for a flip or change of orientation onthe landing surface. In other cases, the UAV may not be able to flip orchange its orientation on the landing surface. Thus, instead of flippingor changing orientation on the landing surface, it may be desirable toallow the UAV to take off with its current orientation away from thelanding surface, and then flip or change its orientation when it isairborne. For example, the landing surface may be determined to be toosmall for a flip or change of orientation. In some cases, the landingsurface may not be flat or even so that a flip or change of orientationmay be difficult. As another example, the landing surface may be movingvery fast or slippery so that a flip may be difficult. The UAV maydetect environment surrounding it (especially the landing surface)and/or its orientation to automatically determine if a flip or change oforientation is suitable on the landing surface or not. If not, the UAVmay take off first and then flip in the air when it receives a signalfrom a user, a controller, and/or a terminal, or alternatively when itdetects a threshold condition. As an example, the environment (e.g.location) can be determined based on a number of GPS satellites incommunication with the GPS sensor. As another example, the environmentcan be determined based on time-of-flight data obtained by the lidarsensor. As another example, the environment type (obstacles in flightroute) can be determined based on image data obtained by the visionsensor, such as an exposure time associated with the image data obtainedby the vision sensor.

In some cases, the UAV is capable of taking off from an underlyingsurface in the first orientation and in the second orientation. In somecases, the UAV is capable of hovering or flight when in the firstorientation and in the second orientation.

The UAV and methods disclosed herein may generate lift for the UAV bycontrolling the directions of the first (e.g. 1, 4 in FIG. 6) set andsecond set (e.g., 2, 3 in FIG. 6) of rotating components of the one ormore propulsion units to generate a lift for the UAV. Each rotatingcomponent disclosed herein may include a rotor blade or a set of rotorblades (or rotor blades). In some embodiments, the UAV and methodsdisclosed herein may include generating a lift for the UAV when the UAVis taking off from an underlying surface when the UAV is in the firstorientation or the second orientation (top panel in FIG. 5).

For a take-off from a landing surface 506, it may occur after any typesof UAV actions that resulted in the UAV being on the landing surface.Non-limiting examples includes a successful flip, an attempted butfailed flip, a landing, powered on but idling on the landing surface,moving along the landing surface, a crash to the landing surface, or thelike. For a take-off from a landing surface, the UAV may take a sequenceof actions that let the UAV move away from the surface. In some cases,the UAV may hover on the landing surface followed by flying withvertical movements. As another example, the UAV may fly directly awayfrom the landing surface with a combination of vertical, horizontal,and/or curved movements.

The take-off may occur automatically with or without the aid of one ormore sensors. The UAV may determine if a flip or change of orientationis necessary based on its current orientation and the landing surface.If a flip or change of orientation is desired but the landing surface,the surrounding environment, and/or the condition of the UAV may be notsuitable for a flip or change of orientation on the landing surface, theUAV may automatically determine to take-off from the landing surface.The take-off may be controlled by a user, a controller, and/or aterminal. The UAV may take-off after it receives a signal from a user, acontroller, and/or a terminal.

In some cases, a signal (either from a remote control and/or terminal orfrom the UAV) may be provided to one or more corresponding propulsionunits, thereby controlling directions of rotation of a first set ofrotating components and a second set of rotating components of the oneor more propulsion units. The signal may be generated upon detection ofa threshold condition 508 using one or more sensors as disclosed herein.As an example, a height threshold can be determined based on a number ofGPS satellites in communication with a GPS receiver onboard the UAV. Asanother example, an obstacle within a threshold distance to the UAV maybe detected using an ultrasound sensor.

The UAV may flip or change orientation when the threshold condition 508is detected or met. A threshold condition may be one or more conditionsthat may occur to the UAV or elements therewithin when accidentalconditions such as a malfunction, a loss of power, a loss ofcommunication, a loss of control, encounter of obstacle(s) or resistanceoccur. The threshold condition may be user-selected or pre-programmedinto the UAV. A threshold condition may be entered into the UAV beforeor during an operation of UAV. The threshold condition may vary orremain constant during operation of the UAV. In some instances, thethreshold condition may adaptively change based on the surroundingenvironment of the UAV. The threshold condition may be set or changed byat least one of a processor, a smart device, a controller, a terminal, adigital processing device, a cloud, a database, an algorithm, anapplication, computer software, a user, a manufacturer of the UAV, orthe like.

As an example, a threshold condition 508 may be met when an externalobject is detected within a pre-determined distance of the UAV.Alternatively, a threshold condition may be met when the UAV contacts anexternal object. Optionally, a threshold condition may include analtitude, a height, acceleration, latitude, or a speed of the UAVgreater than or less than a predetermined value. A threshold conditionmay be detecting a rotational speed of rotor blade(s) to be less than orgreater than a pre-selected speed. As another example, a thresholdcondition may be detecting a predetermined change in altitude, height,acceleration, latitude, speed of the UAV greater than or less than apredetermined value within a certain period of time. As another example,a threshold condition may be failure to achieve a predetermined changein altitude, height, acceleration, latitude, speed of the UAV greaterthan or less than a predetermined value within a preselected period oftime. A threshold condition may be detecting a predetermined change inrotational speed of at least one rotor blades to be less than or greaterthan a pre-selected speed. A threshold condition may be failure toachieve a predetermined change in rotational speed of at least one rotorblades to be less than or greater than a pre-selected speed. As anotherexample, the UAV may flip or change its orientation after an unwantedchange in orientation is introduced by external sources, for example, astrong wind.

The UAV may detect a threshold condition 508 using one or more sensingunits or sensors as disclosed herein. Each of the sensors may be locatedon the UAV, at one or more different locations of the UAV, or remotelyaway from the UAV. A sensor may be located on one or more differentlocations including: the central body 102, the rotor 110 a, 110 b, theprotective cover 106, and the support 108. Each sensor may directlysense one or more properties of the UAV or the environment surroundingthe UAV. Alternatively, each sensor may sense and convert sensing data(by itself or by other digital processing devices onboard the UAV orremotely located from the UAV) into one or more properties of the UAV orof the environment surrounding the UAV. Non-limiting examples of such aproperty may be a flight orientation, a spatial disposition, a velocity,an altitude, latitude, acceleration, a speed, a tilt angle, a height,and a distance to an external subject. In some instances, propertiesindirectly or directly sensed by a sensor are up to three degrees oftranslation and up to three degrees of rotation. The one or more sensorsmay include global positioning system (GPS) sensors, motion sensors,inertial sensors, proximity sensors, ultrasonic sensors, infraredsensor, ultraviolent sensor, image sensors, electromagnetic emissionsensors, radar, or any other sensors. As an example, the GPS sensor maysequentially sense a position of the UAV on a landing surface 506 andthen one or more positions of the UAV while flying, then a processor, acontrol unit, or the like may compare positions of the UAV at differenttime points to determine a height or a distance of the UAV to thelanding surface 506. The detected height may be compared to a thresholdheight and see if the threshold condition has been met or not.

Alternatively, a sensor can be used to provide data regarding theenvironment surrounding the UAV, such as weather conditions, proximityto potential obstacles, location of geographical features, location ofmanmade structures, a wind speed, a wind direction, a rain speed, atemperature, and the like. Such environmental data may be up to threedegrees of translation and up to three degrees of rotation. For example,the one or more sensors may sense the relative position of the bottomportion 502 to the top portion 504 of the UAV, and determines theorientation using a pre-defined database correlating positions of bottomand top portions to different orientations.

The UAV may sense its orientation (e.g., 500 a or 500 b), or a change oforientation using one or more sensing units. The sensing unit may be asensor as disclosed herein. The sensing unit may be any number ofsensors. The sensing unit may be located on the UAV or off-board of theUAV. In some cases, the sensing unit is a combination of any number ofsensors on the UAV and any number sensors off from the UAV. The sensorsmay directly sense data selected from: position, position change at twotime points, translational velocity, translational velocity change attwo time points, translational acceleration, change in translationalacceleration at two time points, orientation, angular velocity, changein angular velocity at two time points, angular momentum, change inangular momentum at two time points, angular acceleration, change inangular acceleration at two time points, rotor blades speed, rotorblades frequency, rotating direction of rotor blade(s) or anycombinations thereof up to three degrees of translation and up to threedegrees of rotation. The sensors may sense data that may be used toderive or generate information regarding the above-listed data. Datasensed by and collected from the sensors are optionally processed sothat they may be analyzed at a certain confidence level. The processedor unprocessed raw data from one or more sensors may be analyzed toyield orientation of the UAV. The optional processing or analysis ofdata may include any data processing methods that may be selected frombut may not be limited to: de-noise, segmentation, pattern recognition,statistical analysis, truncation, filtering, sampling, algebraicoperation, frequency analysis, thresholding, compression, decompression,encryption, decryption, and signal transformation.

Being able to determine whether a threshold condition 508 has been metwithout requiring any external signals may advantageously permit the UAVto operate independent of many environmental factors. For example, notrequiring a GPS input may permit the aerial vehicle to operate in indooror outdoor conditions where GPS signals may otherwise be blocked orunreliable. In another example, not requiring feedback from outside thevehicle (for example, sensors that may require an echo to determinealtitude of the UAV), may diminish risks of interfering signalsoccurring, or having environmental factors such as moving parts (forexample, leaves blowing in the wind) reducing the reliability of theechoed signal. The systems and methods described herein are also simpleand do not require very many complicated calculations that can take moretime or processing power. The systems and methods provided herein mayprovide conditions that may be easily evaluated without performingcomplex calculations that may be used in systems that look at variousrelative position and movement information compared to an outsidereference. The UAV may determine whether the threshold condition is metor not based on information that is provided on-board the aerial vehiclewithout requiring external signals. This may provide a smooth, assistedtakeoff-then-flip or flip-then-take-off sequence of actions for the UAVin a wide variety of environmental conditions.

Threshold conditions 508 with or without combination of one or moreproperties of the UAV or its environment may trigger different controlto achieve a flip. Such difference in control to achieve a flip mayprotect the UAV from failure in actions and/or possible damages causedby the failure, thus increase the reliability and safety of the UAV andthe elements therewithin. In some cases, when a UAV reaches a thresholdheight, the UAV may automatically control to flip in an optimal speedranging when the wind resistance is low, and the lift is sufficient. Asanother example, when a UAV detects a threshold wind resistance or windspeed, it may automatically flip in a direct so as to reduce windresistance during operation. As another example, when reaching athreshold condition of touching an external object, the sensors maydetect where the external object is with respect to the fly route, andthe UAV may flip and result in a location away from the external object.Such control may be automatic with assistance from the sensor(s) or byexternal control from a user.

The flip may be controlled or effected without damaging impact to theUAV by the motion. The flip may be controlled or effected based on theweight, size, shape of the UAV, and/or maximal speed of the propulsionunits so that the flip does not cause damages to the UAV or its elementstherewithin.

With control of one or more rotor blades separately or together, theflip of the UAV may be controlled or effected. In particular, thecontrol of one or more rotor blades may include the rotating speed ofone or more rotor blades and the direction of rotation of one or morerotor blades. Further control of the rotor blades may include the bladepitch of one or more rotor blades. As an example, rotor blades ofpropulsion units on the top left and bottom right of the UAV may becontrolled to rotated in a clockwise direction at two different speeds,and the rotor blades of propulsion units on the top right and bottomleft side of the UAV may be controlled to rotate in a counter clockwisedirection at a same speed (when viewed from the top or the bottom of theUAV), and the speed of each propulsion unit may be controlled so thatthe top-left side of the UAV rolls upward at a constant speed while thebottom right of the UAV rolls downward and finally cause a flip of theUAV about an axis within the x-y plane (as in FIG. 1).

The flip of the UAV may result in rotational movement, translationalmovement, horizontal movement, vertical movement or their combinationsto the UAV. The central body of the UAV may be at a different or a samelocation in three dimensions after a flip. During the flip, the UAV mayhave translational movement, rotation movement, horizontal movement,vertical movement or their combinations.

The UAV may automatically detect the threshold condition 508 withoutexternal signals. Automatic control of the UAV's flip may beadvantageous so that the effect of action is not limited by the user'seyesight, and the may not be influenced if the UAV is out of the datacommunication range or if the user is novice. Such automatic detectionmay be fast as the communication is only within the UAV, it may be moreefficient and simpler as it does not require any external input and/orcontrol, and/or it may be more reliable as failure in communication tothe external control or in the external control does not affect theautomatic detection at the UAV.

Manual control of the UAV's flip may be advantageous when one or moreelements of the automatic detection fail under different circumstances.Manual control of the flip may be advantageous when the user isexperienced. Manual control of the flip may be advantageous when theuser has a better perception of surrounding environment. Manual controlof the flip may be advantageous when the surrounding environment is toocomplicated for automatic control to handle or automatic control is ableto perform a flip.

FIG. 6 shows a schematic view of a UAV changing its orientation duringflight, in accordance with embodiments of the present disclosure.

The embodiment in FIG. 6 may be similar to the embodiment in FIG. 5except for the following differences. In FIG. 6, the UAV may changeorientation while in flight, at a height greater than threshold heighth6 to an underlying surface 606, to a second flight orientation 600 bthat may not be about 180 degrees different from the first flightorientation 600 a and above an underlying surface. The UAV may resumeflying at the second flight orientation. During the flip 612, the UAVmay include an intermediate flight orientation 600 c that may be 90degrees different from the first flight orientation and less than 90degrees different from the second flight orientation.

The second flight orientation may be about 91, 100, 110, 120, 130, 140,150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, or 269degrees different from the first flight orientation. Alternatively, thesecond flight orientation may at any angle greater than 1 degree fromthe first orientation. The intermediate flight orientation may be at anyangle that is smaller than the difference between the first and thesecond flight orientation. An angle of flip 612 may range from about 91to about 269 degrees. A radius of an arc (defining the UAV's motion pathduring the flip) may range from about 0.2 meter to about 0.5 meters. Theheight h6 may range from about 0.2 meters to about 0.6 meters above theunderlying surface.

A second flight orientation with various angle differences to the firstflight orientation may be advantageous for avoiding external obstaclesand for resuming flight in various directions and along different flightpaths.

FIG. 7 shows a schematic view of a UAV changing its orientation whenflipping from an upward sloping surface to a horizontal landing surface,in accordance with embodiments of the present disclosure.

The embodiment in FIG. 7 may be similar to the embodiment in FIG. 2except for the following differences. In FIG. 7, the UAV in the firstorientation 700 a may be configured to flip from a first inclinedsurface 706 a to a horizontal surface 706 b in a second orientation 700b. The first inclined surface may be sloped in an upward manner from thehorizontal surface by about 30 degrees. An angle of flip 712 may rangefrom about 89 to about 179 degrees. A radius of arc (defining the UAV'smotion path during the flip) may range from about 0.2 meters to about0.6 meters.

In some embodiments, the UAV may be in contact with the horizontalsurface after the flip. During the flip, the UAV may include anintermediate flight orientation 700 c that may be less than 90 degreesdifferent from the first flight orientation and less than 90 degreesdifferent from the second flight orientation. Alternatively, theintermediate flight orientation may be at any angle that is smaller thanthe difference between the first and the second flight orientation.

FIG. 8 shows a schematic view of a UAV changing its orientation whenflipping from an upward sloping surface to mid-air, in accordance withembodiments of the present disclosure.

The embodiment in FIG. 8 may be similar to the embodiment in FIG. 7except for the following differences. In FIG. 8, the UAV in the firstorientation 800 a may be configured to flip from a first inclinedsurface 806 a to be in a second orientation 800 b. The first inclinedsurface may be sloped in an upward manner from the horizontal surface byabout 30 degrees. The UAV may be configured to flip from the firstinclined surface to be in flight at a height h₈ above the surface 806 b.An angle of flip may range from about 89 to about 179 degrees. A radiusof arc (defining the UAV's motion path during the flip) may range fromabout 0.2 meters to about 0.6 meters. In the embodiment of FIG. 8, theUAV may be in the air and need not be in contact with the horizontalsurface 806 b after the flip. During the flip, the UAV may include anintermediate flight orientation 800 c that may be less than 90 degreesdifferent from the first flight orientation and less than 90 degreesdifferent from the second flight orientation. Alternatively, theintermediate flight orientation may be at any angle that is smaller thanthe difference between the first and the second flight orientation.

FIG. 9 shows a schematic view of a UAV changing its orientation whenflipping from a downward sloping surface to a horizontal landingsurface, in accordance with embodiments of the present disclosure.

The embodiment in FIG. 9 may be similar to the embodiment in FIG. 7except for the following differences. In FIG. 9, the UAV in the firstorientation 900 a may be configured to flip from a first declinedsurface 906 a to a horizontal surface 906 b in a second orientation 900b. The first declined surface may be sloped in a downward manner fromthe horizontal surface by about 35 degrees. The UAV may be configured toflip from the first declined surface to the horizontal surface. An angleof flip may range from about 181 to about 269 degrees. A radius of arc(defining the UAV's motion path during the flip) may range from about0.2 meters to about 0.6 meters. In some embodiments, the UAV may be incontact with the horizontal surface after the flip. The UAV may thenresume flying in the second flight orientation from the horizontalsurface. During the flip, the UAV may include an intermediate flightorientation 900 c that may be greater than 90 degrees different from thefirst flight orientation and greater than 90 degrees different from thesecond flight orientation. Alternatively, the intermediate flightorientation may be at any angle that is smaller than the differencebetween the first and the second flight orientation.

FIG. 10 shows a schematic view of a UAV changing its orientation whenflipping from a downward sloping surface to mid-air, in accordance withembodiments of the present disclosure.

The embodiment in FIG. 10 may be similar to the embodiment in FIG. 9except for the following differences. In FIG. 10, the UAV in the firstorientation 1000 a may be configured to flip from a first declinedsurface 1006 a to a horizontal surface 1006 b in a second orientation1000 b. The first declined surface may be sloped in a downward mannerfrom the horizontal surface by about 25 degrees. The UAV may beconfigured to flip from the first declined surface to the horizontalsurface. An angle of flip may range from about 181 to about 269 degrees.A radius of an arc (defining the UAV's motion path during the flip) mayrange from about 0.2 meters to about 0.6 meters. In the embodiment ofFIG. 10, the UAV may be in flight and need not be in contact with thehorizontal surface after the flip. The UAV may then resume flying in thesecond flight orientation at a height h₁₀ above the horizontal surface.During the flip, the UAV may include an intermediate flight orientation1000 c that may be greater than 90 degrees different from the firstflight orientation and greater than 90 degrees different from the secondflight orientation. Alternatively, the intermediate flight orientationmay be at any angle that is smaller than the difference between thefirst and the second flight orientation.

FIG. 11 shows a schematic view of a UAV changing its orientation inresponse to a user command, in accordance with embodiments of thepresent disclosure.

A user 1110 may communicate with a UAV using a controller 1106. The UAVinitially in a first flight orientation 1100 a with its bottom portion1102 facing upward, and its top portion 11011 facing downward mayreceive a wireless signal 1108 from the user 1110 and may flip into asecond flight orientation 1100 b with its bottom portion 1102 facingdownward, and its top portion 1104 facing upward and resumes flyingafter the flip. The user command may initiate the flip of the UAV whilethe UAV may be on the ground, taking off, landing, or flying regularly.

The UAVs and/or the methods disclosed herein may include a signal thatis indicative of a user input to initiate the flip of the UAV. The userinput is provided via a user terminal remote 1106 to the UAV. In somecases, the signal is generated at the user terminal and transmitted viaone or more communication channels 1108 from the user terminal to theUAV. In some cases, the user input to initiate the flip may only becapable of initiating the flip and no other actions by the UAV. Infurther cases, the flip of the UAV from the first orientation 1100 a tothe second orientation 1100 b causes a change in at least 170 degrees ofthe orientation of the UAV. The first orientation may be for the UAV tobe upside down while the second orientation may be for the UAV to beright side up. In some cases, the user input may be a single action thateffects the flip of the UAV from the first orientation to the secondorientation. The signal indicative of the user input may be obtainedwhile the UAV is on an underlying surface or in flight.

The UAV may comprise one or more protectors that prevent the one or morepropulsion units from directly contacting the underlying surface

With control of one or more rotor blades separately or together, theflip of the UAV may be controlled or effected, either automatically ormanually by a user 1110 via a remote control 1106. In particular, thecontrol of one or more rotor blades may include the rotating speed ofone or more rotor blades and the direction of rotation of one or morerotor blades. For example, rotor blades on the top left and bottom rightof the UAV (as 1 and 3 shown in FIG. 6) may be controlled to rotated ina clockwise direction in a first speed or in two different speeds, andthe rotor blades on the top right and bottom left side of the UAV (as 2and 4 in FIG. 6) may be controlled to rotated in a counter clockwisedirection in a second speed or in two different speeds (when viewed fromthe top of the UAV), and the speed of each set of rotors on the samepropulsion unit may be controlled so that the top-left side of the UAV(as 1 shown in FIG. 6) moves higher along the yaw axis (z axis inFIG. 1) than the other propulsion units.

The flip of the UAV may result in rotational movement, translationalmovement, horizontal movement, vertical movement or their combinationsto the UAV. The UAV may be at a different or a same position in threedimensions after a flip. During the flip, the UAV may have translationalmovement, rotation movement, horizontal movement, vertical movement ortheir combinations.

The controller or terminal 1106 may include a user interface such as akeyboard, mouse, joystick, touchscreen, a microphone, an electronicdisplay, or the like. Any user input can be used to interact with thecontroller, such as manually entered commands, voice control, gesturecontrol, voice control, eye movement, or position control (for example,via a movement, location or tilt of the terminal).

Different type of actions of the user 410 may initiate the flip. Asingle action by the user may initiate the flip process. In some cases,the single action is the selection of a button or touchscreen of aterminal remote to the UAV. Alternatively, the single action may be theflip of a switch on a terminal remote to the UAV, a verbal command thatis registered by a terminal remote to the UAV, a change in attitude of aterminal remote to the UAV, or any actions. Alternatively, a manualprocess with user-controlled motion parameters may initiate how the flipmay occurs. Alternatively, a user may select from a pre-determined listof options to initiate different type of flip with different motionparameters. Alternatively, a user may directly move a joystick or thelike to control correlated movements of the UAV and result in a flip.

The UAV communicates data with the controller or terminal 1106 via acommunication channel 1108. Such communication via the channel may beone-way or two-way. Any channels of communication can be used, such aswired communication channels or wireless communication channels. Forexample, communication may use one or more of local area networks (LAN),wide area networks (WAN), infrared, radio, Wi-Fi, point-to-point (P2P)networks, telecommunication networks, cloud communication, Bluetooth andthe like. Optionally, relay stations, such as towers, satellites, ormobile stations, can be used. Wireless communications can be proximitydependent or proximity independent. In some embodiments, line-of-sightmay or may not be required for communications.

There are advantages with user-controlled flip of the UAV. In somecases, when the camera only captures views from certain angles of theUAV, the user may flip the UAV and choose to flip the UAV to captureimages that would otherwise not be able to get. In alternative cases,when the UAV is outside of the eyesight of the user, the user may chooseto flip the UAV and enable the UAV to automatically return to the userwith the flip and the correspondingly reversed flying route. As anotherexample, when the UAV experiences some dysfunction with a protectivecover at its bottom edge and may be unable to land properly in a currentorientation, the user may choose to flip the UAV and uses the protectivecover's top edge for protected landing after a flip. As another example,when the UAV may get trapped by external objects and cannot resumeflying by its automatic controls, the user may initiate an auto-returnfunction of the UAV so that the UAV may revert its route back to whereit starts. FIG. 12 illustrates a schematic view of a flight controlsystem of a UAV that is capable of effecting a change in orientation ofthe UAV, in accordance with embodiments of the present disclosure.

A UAV may include a flight control unit 1202 which delivers controlcommand(s) to one or more electronic speed controls (ESCs) 1204 a, 1204b. An ESC 1204 a may interpret the control command(s) received from theflight control unit 502 and thereby control a propulsion unit 1206 a, aprotective cover 1208 a, a plurality of rotor blades 1210 a, and anactuator 1212 a for the rotor blades 1210 a. Additionally, the flightcontrol unit may control communication to a remote controller, optionallanding gear, and/or one or more sensors of the UAV.

The UAV disclosed herein may include one or more processors (e.g.located at the flight control unit or one or more ESCs), individually orcollectively configured to generate a signal that causes the UAV to flipfrom a first orientation to a second orientation opposite the firstorientation; and one or more propulsion units that effect the flip ofthe UAV from the first orientation to the second orientation in responseto the signal.

A flight control unit 1202 may include one or more components thatenable its control of the UAV and one or more elements therewithin. Theflight control unit may include one or more selected from: a digitalprocessing device, a processor, a digital filter, a data communicationlink, a power source, a computer memory, a database, an algorithm, anoperation system, a computer program, an application, a software module,a non-transitory computer media, or the like. The flight control unitmay be on-board the UAV in order to allow fast communication andefficient control of the UAV from the unit. A flight control unit may belocated on one or more different locations including: the central body,the propulsion unit 1206 a, 1206 b, the rotors 1210 a, 1210 b, theprotective cover 1208 a, 1208 b, and the structural support.Alternatively, the flight control unit may be off-board the UAV toreduce weight, reduce possible damages during UAV operation, and/orremove possible constraints to the flight control unit, such constraintsmay include but are not limited to the size, weight, power supply, andprocessing speed of the control unit.

The flight control unit may include one or more one or more processorsconfigured to individually or collectively control direction of thefirst set of rotating components and the second set of rotatingcomponents of the one or more propulsion units. In some cases, theprocessor may be configured to generate a signal to control one or morepropulsion units. In some cases, a signal from the one or moreprocessors is configured to cause the UAV to change orientations betweenthe first orientation and the second orientation.

A flight control unit 1202 may communicate with the one or more sensors,the controller, and/or terminal in two-way communication. A flightcontrol unit 1202 may receive data from one or more sensors, processdata from one or more sensors, store signal from one or more sensors,and/or generate control signal to control one or more propulsion units.Alternatively, a flight control unit may receive signal(s) from one ormore controller or terminal, process signal from one or more controlleror terminal, store signal from one or more controller or terminal,and/or generate control signal (s) to one or more propulsion units. Aflight control unit may automatically generate a control signal to theESC 1204 a, 1204 b based on data received from one or more sensors orone or more terminals. Alternatively, a flight control unit may delivermanual signal from a terminal or a controller to form a control signalto the rotors. In some cases, data processing at the flight control unitmay include but may not be limited to: noise reduction, signalsegmentation, filtering, sampling, algebraic operation of one or moresignals, frequency analysis, thresholding, compression, decompression,encryption, decryption, signal transformation, or the like. A flightcontrol unit may also receive data from one or more propulsion units,process data from one or more propulsion units, store data from one ormore propulsion units, or transmit data to one or more sensors,controllers, and/or terminals. Such communication may a feed-back of theUAV operation.

The UAV may include an electronic speed control (ESC) unit 1204 a, 1204b that communicates directly with the flight control unit 1202 as wellas one or more propulsion units 1206 a, 1206 b, and element(s)therewithin. The ESC may or may not be part of the flight control unit.The ESC may or may not be physically located at or in close vicinity tothe flight control unit. An ESC may be located on one or more differentlocations including: the central body, the propulsion unit 1206 a, 1206b, the rotors 1210 a, 1210 b, the protective cover 1208 a, 1208 b, andthe structural support. Alternatively, the ESC may be off-board the UAVto reduce weight, reduce possible damages during UAV operation, and/orremove possible constraints to the ESC, such constraints may include butare not limited to the size, weight, power supply, and processing speedof the control unit. The ESC may communicate with the one or moresensors, the controller, and/or terminal directly or indirectly (with anintermediator, e.g., with the flight control unit 1202). Thecommunication from or to the ESC may be one-way or two-way. Thecommunication may be one way from the flight control unit to the ESCthen to one or more propulsion units and its element(s) therewithin. Thecommunication may be two-way so that the speed at the one or morepropulsion units and its element(s) therewithin may be detected by theESC and then communicated to the flight control unit.

The ESC may include one or more one or more processors configured toindividually or collectively control direction of the first set ofrotating components and the second set of rotating components of the oneor more propulsion units. In some cases, the processor may be configuredto generate signal to control one or more propulsion units. In somecases, a signal from the one or more processors is configured to causethe UAV to change orientations between the first orientation and thesecond orientation. In some cases, the signal is provided to the one ormore corresponding propulsion units by one or more ESC units, said ESCunits configured to individually control speeds and/or directions of oneor more corresponding rotating components of the one or more propulsionunits. In some cases, the signal from the one or more ESC units isconfigured to cause the UAV to change orientations between the firstorientation and the second orientation. In some cases, the one or morerotating components include rotor blades. In some cases, the firstorientation is for the UAV to be upside down. In some cases, the secondorientation is for the UAV to be right-side up.

The ESC 1204 a, 1204 b may translate a comprehensive signal from theflight control unit into separate speed control signals so that at leastone element of at least one propulsion unit can be controlled by theESC. The ESC or the flight control unit 1202 may use existing or currentspeed, position, orientation, voltage, current, and/or power data asinput, future speed, position, orientation, voltage, current, and/orpower data as output, and calculate the parameter(s) for element(s) ofthe propulsion unit that may change the input data into the output dataof the UAV. The time duration to complete the speed control process maybe another input for the ESC to consider. The ESC may include afeed-back system to control the speed of the propulsion units. As anexample, if the current speed of rotor blades 1210 a in one propulsionunit 1206 a is 1000 rounds per minute (rpm) with an actuator power of10, the ESC compares the future speed to 1000 rpm, if the future speedsent by the flight control unit is 3000 rpm, the ESC may increase thepower level to 30. Alternatively, the ESC may gradually increase powerand detects the rotor blade speed in real time, and then adjust poweragain accordingly based on the real-time rotor blades speed until itreaches the speed goal set by the flight control unit. Alternatively,the ESC may search pre-existing look-up database or the like regardingspeed-power relationship and locate the exact power using the desiredspeed.

The ESC 1204 a, 1204 b may be any type of ESCs that may be used forUAVs. The ESC may serve similar purpose as a throttle servo of a glowpowered airplane. The ESC may be electrically and/or electronicallyconnected to a power source (e.g. a battery), the flight control unit1202, and the actuator 1212 a, 1212 b. The ESC may include an electroniccircuit to vary a speed, a direction and possibly also to act as adynamic brake of an actuator 1212 a, 1212 b, thereby controls rotationof the rotor blades 1210 a, 1210 b. The ESC may contain amicrocontroller interpreting the input signal from the flight controlunit 1202 and appropriately controlling the actuator using a built-in orcustomized program. The ESC may have an update rate of about 0.001 Hz toabout 5000 Hz. The ESC may send the output control signal to rotors atconstant or variable update rate. The output signal that the ESC sendsto the motor(s) may be alternating current signal with specificalternating frequency and voltage level(s). The output signal may alsohave different phases. In some cases, the ESC may accepts a 50 Hz inputsignal from the flight control unit 1202 or servo whose pulse widthvaries from 1 millisecond (ms) to 2 ms. When supplied with a 1 ms widthpulse at 50 Hz, the ESC may responds by turning off the actuatorattached to its output. A 1.5 ms pulse-width input signal may drive theactuator at approximately half-speed. When presented with 2.0 ms inputsignal, the motor may run at full speed. The input signal that the ESCreceives from the flight control unit 1202 may be alternating currentsignal with specific voltage level(s). The output signal may also havedifferent phases. Alternatively, the input signal may be any electricalor electronic signals that may be translated at the ESC to outputwaveform signals.

Each ESC 1204 a, 1204 b may be positioned at different locations of theUAV. In some embodiments, the ESC may be located at the central body, atthe protective cover 1208 a, 1208 b, at the optional arm extending fromthe central body and supporting the propulsion units 1206 a, 1206 b, atthe propulsion units, at the actuator 1212 a, 1212 b, at optionallanding gear, or any other locations of the UAV. Each propulsion unit1206 a, 1206 b may include an arbitrary number of rotor blades 1210 a,1210 b In some cases, each propulsion unit includes an even number ofrotor blades. In some cases, each propulsion unit includes at least 2,4, or 6 rotor blades. Each rotor blade of the same propulsion unit isattached to the actuator 1212 a, directly or indirectly to a sameactuator at its proximal end (e.g. as shown in FIG. 1). And the totalnumber of rotor blades distributes evenly along a circular area. As anexample, 4 rotor blades may be 90 degrees apart from its neighboringrotor blades and are evenly distributed. The distal end of each rotorblades extends outwardly. Each rotor blade has a top surfacesubstantially facing upward in the UAV's initial taking-off orientation(with or without a tilt angle), and a bottom surface substantially facedownward (with or without a tilt angle) when the top part of the UAV isfacing upward. There may be a tilt angle between a horizontal plane andthe top or the bottom surface, when the UAV is substantially in ahorizontal plane.

The UAV may include one or more protective covers 1208 a, 1208 b thatprevent the one or more propulsion units from directly contacting anexternal object. The UAV may include at least a protective cover 1208 a,1208 b for one propulsion unit 1206 a, 1206 b. In some cases, a heightof the one or more protective covers is greater than a height of acentral body of the UAV. In some cases, a height of the one or moreprotective covers is greater than a height of the one or more propulsionunits. In some cases, each of the one or more protective covers 1208 a,1208 b . . . forms a tunnel around a corresponding propulsion unit ofthe one or more propulsion units. In some cases, the protective coverprotects the rest of the elements of the propulsion unit from damages orundesired impact from external sources when the UAV is flying, landing,taking off, and/or changing directions. The protective cover may haveany three dimensional geometrical shape that includes a tunnel around acorresponding propulsion unit of the one or more propulsion units, ascan be seen as 106 in FIG. 1. In some cases, each protective covercomprises a sleeve in which a propulsion unit is disposed. In somecases, the one or more protective covers permit the one or more rotatingcomponents of the one or more propulsion units to rotate in the firstdirection or the second direction when the UAV is on an underlyingsurface. The rotating component may include a rotor (or rotor blades), aset of rotor(s), and/or a motor actuating the rotor(s). The tunnel orsleeve is not covered at its top and its bottom but covered andsupported along its longitudinal direction from its top to the bottom.The other elements of the propulsion unit may be enclosed in thetunnel/sleeve of the protective cover. The other elements may be alsolocated toward the center of the chamber along the longitudinaldirection in order to provide optimal protection, support, and/or weightdistribution of the propulsion unit. The protective cover in someembodiments has a cylindrical shape. The protective cover may have otherthree-dimensional shapes. Examples include a cubic, a cuboid, afoot-ball shape, a spindle shape, an hour-glass shape, an ovoid, or thelike. The protective may have one or both of its top and bottom facesnot covered completely in order to allow proper venting and air flowfrom within the protective cover to outside of the protective cover.

Each propulsion unit 1206 a, 1206 b may include an actuator 1212 a, 1212b for driving rotation of the rotor blades. The actuator may be coupledto the one or more rotor blades with aid of a shaft. Rotation of theactuator may cause rotation of the shaft, which may in turn causerotation of the rotor blades. Any description of a shaft may also applyto multiple shafts that may be driven by the same actuator. The actuatormay be a motor. Any driving mechanism can be used for the actuator, suchas a DC motor (as, brushed or brushless), AC motor, stepper motor, servomotor, and the like. The movement can be actuated by any actuationmechanism, such as an engine or a motor. The UAV can include one or moreengines, motors, wheels, axles, magnets, rotors, propellers, blades,nozzles, or any combination thereof. Further, different actuators maywork dependently or independently with each other to actuate individualpropulsion units for different rotational movements. In someembodiments, propulsion unit 1206 a may be actuated to have an oppositerotational direction and a different rotational speed as propulsion unit1206 b. Such differences allowed by the actuator(s) of the UAV maygreatly facilitate the UAV in its proper function especially its changeof flight orientations.

Each propulsion unit 1206 a, 1206 b may include a supporting structure.The supporting structure prevents at least a portion of the protectivecover from collapsing. The supporting structure contacts the protectivecover at its inner surface at one end, and contacts the actuator, therotor blade(s), a rotating shaft, and/or other elements within theprotective cover. The supporting structure may be located closer to thecenter than to both edges of the protective cover in the longitudinaldirection of the cover. In some embodiments, at least one ESC isincluded in one propulsion unit. An ESC may be located close to thecenter of the protective cover longitudinally without obstructing therotation of the rotor blades. An ESC may be attached to each rotor bladeclose to or in close vicinity to the proximal end of the blades. In somecases, an ESC is attached to or in close vicinity to the actuator, orthe rotating shaft. In some cases, at least two ESC is included, oneattached or in close vicinity to a rotor blade(s), the other attached toor in close vicinity to an actuator or a rotating shaft.

The UAV may change orientation, speed, or flying direction by control ofrotational speed and/or direction of one or more propulsion units 1206a, 1206 b. The UAV may change orientation, speed, or flying direction bycontrol of rotational speed and/or direction of one or more rotorblades. With control of each propulsion unit separately or together, theflipping type, and the flipping velocity of the UAV may be controlled.For example, for each propulsion unit, the rotor speed, and the rotordirection may be controlled individually. For a UAV with four propulsionunits, eight individual parameters may be controlled independently or ina combination of any integer between two and eight, resulting in a greatvariety of possible combination of rotating speed and directions in oneto four propulsion units. By using these different combinations, theorientation, speed, flying direction, acceleration, lift, or otherproperties of the UAV as mentioned above may be controlled. As anexample, in detection of an obstacle to the left side of the UAV, theUAV may increase the rotational speed of two propulsion units on theleft-side of the UAV so that the left side may be lifted further up thanthe right side to avoid the obstacle. As another example, when the UAVhits an obstacle and flipped accidentally, the UAV may automaticallyrevert the rotation direction of all propulsion units and increase therotational speed of propulsion units on the left side so that it ishigher than the speed of propulsion units on the right, the left side ofthe UAV lift up fast enough and initiate a 180-degree flip of the entireUAV. The rotational speed and direction of each propulsion unit may beadjusted during the flip and after the UAV is flipped.

The flipping velocity may have a constant magnitude with a varyingdirection. The flipping velocity may be varying in both its magnitudeand direction. The magnitude of flipping velocity may include any shapeof waveform that starts from zero at the onset of flipping and ends atzero at the end of flipping.

FIG. 13 illustrates a schematic view of the rotation directions ofpropulsion units of a UAV when the UAV is in different orientations, inaccordance with embodiments of the present disclosure.

The UAV may have four propulsion units 1, 2, 3, and 4 extending from thecentral body 1302. When viewed from the top, a first propulsion unit 1may extend from the top-left of the central body, a second propulsionunit 2 may extend from the top-right of the central body, a thirdpropulsion unit 3 may extend from the bottom right of central body, anda fourth propulsion unit 4 may extend from the bottom left of thecentral body. Two propulsion unit 1 and 3 may rotate clockwise while theother two propulsion units 2 and 4 may rotate counter clockwise when theUAV is in the right-side orientation (i.e., the top side of the UAV isfacing upwards). When the UAV is flipped 1312 about a flipping axis 1305to be in an upside down orientation (bottom right in FIG. 13), thebottom of the UAV may face upward, and the locations of the propulsionunits may be mirrored about the flipping axis 1305. In order for the UAVto take-off or fly when it is in the upside down orientation, thepropulsion units 1 and 3 may rotate counter clockwise while propulsionunits 2 and 4 may rotate in an opposite direction clockwise, as shown inthe bottom right of FIG. 13. Conversely, when the UAV is flipped aboutanother flipping axis 1307 to be in another upside down orientation (topleft in FIG. 13), the bottom of the UAV may face upward, and thelocations of the propulsion units may be mirrored about the flippingaxis 1307. In order for the UAV to take-off or fly when it is in theupside down orientation, propulsion units 1 and 3 may rotate counterclockwise while propulsion units 2 and 4 may rotate in an oppositedirection clockwise, as shown in the top left of FIG. 13.

In some embodiments, the UAV may have at least four propulsion units 1,2, 3, and 4. Similar to a quadrotor helicopter, or quadcopter, the fourpropulsion units may use two sets of rotor blades. The rotor bladeslocated in propulsion units along the same diagonal axis of the UAV maybe in the same set (e.g. 1 and 3, or 2 and 4). The rotating componentsmay be sets of rotor blades. The first set of rotating components (e.g.1 and 3) may be configured to rotate in a first direction and the secondset of rotating components (e.g., 2 and 4) may be configured to rotatein a second direction when the UAV is in a first orientation.Conversely, the first set of rotating components may be configured torotate in the second direction and the second set of rotating componentsmay be configured to rotate in the first direction when the UAV is in asecond orientation opposite the first orientation (left panel and rightpanel). As an example, blades of the top left 1 and bottom right 3propulsion units may rotate clockwise while blades the top right 2 andbottom left 4 propulsion units may rotate counterclockwise when viewedfrom the top of the UAV in the right-side up orientation. When the UAVchanges flight orientation, both sets may change rotating direction suchthat the set initially rotating clockwise may rotate counter-clockwiseand the set initially rotating counter clockwise may rotate clockwise.In some cases, the rotor blades may have a fixed pitch. Two propulsionunits along the diagonal axis of the UAV (top-right to bottom-left ortop-left to bottom-right) may rotate in the same direction at the samespeed or at different speeds. Two propulsion units not on the samediagonal axis of the UAV (top-right to bottom-left or top-left tobottom-right) may rotate in different directions at the same speed or atdifferent speeds. By changing the speed of the motor(s) actuatingindividual set of rotor blades, and thus the rotating speed of each setof rotor blades, a thrust can be generated to propel the UAV in threespatial dimensions, or to generate a desired torque (or turning force)to change the orientation (attitude) of the UAV. For example, a heightof a UAV may be controlled by adjusting the amount of power to all fourmotors. Turning left or right or changing height may be achieved bydecreasing or increasing the speed of individual rotors.

When the UAV is in a different orientation opposite to the right side uporientation, the same rotating direction of the propulsion unit may failto generate lift for the UAV. However, by reversing the rotatingdirection, a lift can be generated for the UAV when it is in thedifferent flight orientation. The reversed direction may be counterclockwise for one or more propulsion units, and clockwise for theremaining propulsion units of the UAV. Alternatively, the UAV may obtainsufficient lift using the rotating direction shown in the bottom rightof FIG. 13 in an upside down orientation. When the UAV is an oppositeflight orientation, and if there are no changes to the rotatingdirection, the UAV may lose its lift and experience a downward drag aswell as gravity. In order to provide lift to the UAV, all the rotorblades may reverse their rotating directions, for example as shown inFIG. 13.

Each set of rotor blade of 1, 2, 3, or 4 may include a pitch. The pitchof the same set of rotor blades along the same diagonal axis of the UAVmay be substantially identical. The pitch of a rotor blade may remainconstant or vary over time in order to adjust the thrust or torque ofthe UAV. The pitch of a rotor blade may be adjusted over timeindependently via the ESC, the flight control unit, a remote control, aterminal, or a combination thereof. As an example, the UAV mayautomatically or by external control vary pitch in flight, to giveoptimum thrust over the maximum amount of the UAV's speed range duringtaking off, landing, flying, and hovering. As another example, low pitchmay be used to yield good low speed acceleration and climb rate duringtake-off while high pitch optimizes high speed performance duringflying.

The rotation of rotor blades may be within one or more planes that maybe substantially parallel to the top surface and/or bottom surface ofthe central body 602 of the UAV. The rotation of rotor blades may bewithin one or more planes that may be substantially vertical to thelongitudinal axis of the protective cover or the z axis as in FIG. 1,and/or substantially parallel to the top edge and/or bottom edge of theprotective cover. The rotation axis of rotor blades may be vertical to ahorizontal plane (x-y plane in FIG. 1). The rotation axis of rotorblades may be vertical to one or more arms 1304 extending from centralbody 602 and supporting the propulsion units 1, 2, 3, 4.

The change in rotational parameters of one or more rotator blades maycause the flip of the UAV. The change in rotational parameters mayinclude one or more selected from: an angle of attack of a rotor blade,a pitch of a rotor blade, a rotating speed of a blade, a rotatingdirection of a rotor blade, or the like. The change of in rotationalparameters of one or more rotator blades may result in change of lift,thrust, torque, flip, or a combination thereof. As an example,increasing rotating speed and/or changing pitch of one or more rotorblades on the right side of the UAV may increase generate a torqueand/or increased lift on the right which may cause a horizontallybalanced UAV to be right side up, top-right side up, or bottom-rightside up, and then UAV may flip about 180 degrees to be up-side down.

The UAV may flip about a flipping axis 1305, 1307 that is parallel to aroll axis or pitch axis of the UAV. The flipping axis may be locatedaway from the UAV. The distance from the UAV to the flipping axis may besubstantially the same before or after the flip 1312. As an example,propulsion unit 1 may have a similar distance to the flipping axisbefore or after the flip.

FIG. 14 illustrates a schematic view of a UAV capable of flipping alonglines that are diagonal to a central body of the UAV, in accordance withembodiments of the present disclosure.

The embodiment in FIG. 14 may be similar to the embodiment in FIG. 13except for the following differences. In FIG. 14, the flipping axis1405, 1407 may be along a diagonal connecting the same set of propulsionunits of the UAV). The flipping axis 1407 may extend between the sameset of propulsion units 1 and 3; and the flipping axis 1405 may extendbetween the same set of propulsion units 2 and 4. The flipping axis maybe within a plane parallel to the x-y plane as shown in FIG. 1. Theflipping axis may be about 45 degrees to the roll and pitch axes of theUAV. The distance from the UAV to the flipping axis 1405, 1407 may besubstantially the same before or after the flip 1412. As an example, thegeometrical center of the central body may have a similar distance tothe flipping axis before or after the flip 1412. The flipping axis maybe overlapping partially with the UAV.

FIG. 15 illustrates a schematic view of a UAV capable of flipping aboutmultiple axes defined with respect to a central body of the UAV, inaccordance with embodiments of the present disclosure.

The embodiment in FIG. 15 may be similar to the embodiment in FIG. 13except for the following differences. In FIG. 15, the flipping axis 1501may be within a plane parallel to the x-y plane as shown in FIG. 1. Theflipping axis may have any arbitrary angle to the pitch, roll, or yawaxes of the UAV. The angle may be any angle in the range of about 0degrees to about 90 degrees. The flipping axis may intersect a centralbody of the UAV. Alternatively, the flipping axis may offset from thecentral body of the UAV. Accordingly, a UAV can be configured to flipabout any axis defined in a three-dimensional space, by adjusting thespeeds and rotational directions of the rotors in the propulsion units.

FIG. 16 provides an illustration of various components of a UAV, inaccordance with embodiments of the present disclosure. The UAV may havea central body 1602 that has a lower height than the protective covers1606. The height of the central body h_(b) may be less than the heightof one or more protective cover h_(pc). When the UAV lands in anorientation (e.g. the right side up orientation) 1600 b, the protectivecover may touch the landing surface using its second portion (e.g.,bottom edges), and the central body 1702 may be located such that itdoes not touch the landing surface when the UAV lands in anyorientation. The width 1604 of the protective cover 1606 may besufficient to include one or more rotor blades 1610 therewithin, andallow them to rotate without touching the longitudinal wall of theprotective cover. The rotor blades 1610 may have a height h_(rb) that issmaller than the height of one or more protective cover, h_(pc), and therotor blades may be located sufficiently to the center of the protectivecover 1606 along its longitudinal direction. The rotor blades 1610 maybe positioned such that they do not touch the landing surface or theprotective cover when the UAV lands in any orientation. The propulsionunit 1604 may be connected to a distal end of an arm extending from thecentral body 1602.

The central body 1602 may have any three-dimensional arbitrary shapethat provides sufficient space to house a payload, a power source, asensor, and/or the like therewithin. The central body may have anyarbitrary shape that provides supports to one or more propulsion unitsor arms attached thereon. Examples of the central body may be a cubic, acuboid, a foot-ball shape, a spindle shape, an hour-glass shape, anovoid, a cylinder or the like. The central body may include interfaceson its surface that allows transformation of one or more arms or one ormore propulsion units between a folded/compact configuration and anextended/flying configuration. In some embodiments, the central body hasa shape and a density that enable a predetermined distribution of weightof the entire UAV. The central body may have an outer surface that isprotected by one or more protective covers. The central body may have anouter surface that does not contact any external subjects that the oneor more protective covers contacts.

In some cases, each propulsion unit is directly attached to the outersurface of the central body 1602. Such attachment may be throughattachment of the protective cover 1606 (e.g. as shown in FIG. 1).Alternatively, each propulsion unit may be attached to the central bodythrough an arm 1612 extending from the outer surface of the centralbody. The proximal end of the arm 1612 may attach to the outer surfaceof the central body 1602 via an optional interface. The distal end ofthe arm may contact the support for the propulsion unit, protectivecover 1606, the hub, the actuator, or their combination via anotheroptional interface.

The UAV may include at least one protective cover 1606 for eachpropulsion unit. The UAV may include at least one protective cover thatprotects two or more propulsion units. The protective cover protects theelements of the propulsion unit from damages or undesired impact fromexternal sources when the UAV is flying, landing, taking off, and/orchanging directions. The protective cover may have any three dimensionalgeometrical shape that includes a tunnel or sleeve in which acorresponding propulsion unit is disposed, as can be seen as 106 inFIG. 1. The tunnel may not be covered at its top and its bottom butcovered and supported along its longitudinal direction from top tobottom. The elements of the propulsion unit (e.g. rotor blades 1610) maybe enclosed in the tunnel of the protective cover. The elements may bealso located toward the center of the chamber along the longitudinaldirection in order to provide optimal protection, support, and weightbalance and/or weight distribution of the propulsion unit. Theprotective cover in some embodiments has a cylindrical shape. Theprotective cover may have other three-dimensional shapes. Examplesinclude a cubic, a cuboid, a foot-ball shape, a spindle shape, anhour-glass shape, an ovoid, a tunnel, a tube, a sleeve, or the like. Theprotective may have one or both of its top and bottom faces not coveredcompletely in order to allow proper venting and air flow from within theprotective cover to outside environment. The wall of the protectivecover may be solid. Alternatively, the wall of the protective cover maybe a frame with any various frame patterns that may provide sufficientsupport to the UAV. The frame protective covers may be used to allowless-limited access to air as compared to solid covers. The frameprotective cover may add less weight to the UAV. The solid protectivecovers may provide more comprehensive protection to the UAV. The solidor frame protective covers may be selected based on different usage ofUAV and different types of environment the UAV mainly flies in. Theprotective covers may have a shape that is asymmetric from its top edgesto bottom edges so that the protective cover looks different when it isup-side down. The protective covers may have a shape that is symmetricwith the plane of symmetry at the central cross-section of theprotective cover along the longitudinal direction. When the UAV flips180 degrees and changes it orientation, the protective cover may lookthe same if it is symmetric. The protective cover may be shaped orconfigured to facilitate same or different thrust in differentorientations. As an example, the tunnel or chamber of the protectivecover may increase the thrust produced by the corresponding propulsionunit therewithin by at least about 5%, about 10%, about 15%, or about20% relative to the thrust produced without the tunnel. Such advantagesof thrust facilitation may be for at least one, two, or more flightorientations of the UAV.

In some cases, each protective cover may include a first portion 1606 aand a second portion 1606 b. In some cases, the first portion of theprotective cover(s) is located above the body 1602 in a direction oflift 1601 generated by the one or more propulsion units when the UAV isin the second orientation 1600 b (e.g., the right side up orientation).In some cases, the second portion of the protective cover(s) is locatedabove the body in a direction of lift (e.g. toward the underlyingsurface) generated by the one or more propulsion units when the UAV isin the first orientation (e.g. the upside down orientation). In somecases, the first portion and the second portion of the protective cover,regardless of the flight orientation of the UAV, may refer to the topand the bottom portions of the protective cover, respectively, when theUAV is in a right-side up orientation positioned along a horizontalplane (e.g., the orientation the UAV initially takes off in).

The protective cover 1606 may include at least a deformable material, atleast a stiff material, and/or at least a non-deformable material. Theprotective cover may include at least a material that has an elasticmodulus of no greater than about 1 gigapascal (GPa). The protectivecover may include at least a material that has an elastic modulus ofbetween about 1 to about 10 GPa. The protective cover may include atleast a material that has an elastic modulus of no less than about 10GPa, about 20 GPa, about 30 GPa, about 40 GPa, about 50 GPa, about 60GPa, about 70 GPa, about 80 GPa, about 90 GPa, or about 100 GPa. Theprotective cover may include at least a material with a modulus ofresilience of less than about 1 pound per square inch (PSi). Theprotective cover may include at least a material with a modulus ofresilience of less than about 5 PSi. The protective cover may include atleast a material with a modulus of resilience of greater than about 5PSi. The protective cover may include at least a material with a modulusof resilience of greater than about 50 PSi. The protective cover mayinclude at least a material with a modulus of resilience of greater thanabout 200 PSi. The protective cover may include at least a material witha modulus of resilience of greater than about 500 PSi. The protectivecover may include at least a material with a modulus of resilience ofgreater than about 2000 PSi.

The protective cover 1606 may have a height of about 2 cm to about 60cm. The central body may have a height of about 1 cm to about 45 cm. Therotor blades may have a height of about 1 cm of about 40 cm. The rotorblades may have a length of about 2 cm to about 35 cm. The central bodymay have a smallest dimension that is about 1 cm to about 40 cm.

Each propulsion unit may include an arbitrary number of rotor blades1610. In some cases, each propulsion unit includes an even number ofrotor blades. In some cases, each propulsion unit includes at least 2,4, or 6 rotor blades. Each rotor blade of the same propulsion unit maybe attached to the actuator directly or indirectly to a same actuator atits proximal end. And the total number of rotor blades of eachpropulsion unit may be separated evenly, and the gap between each twoadjacent rotor blades may be a substantially identical fan shape. As anexample, 4 rotor blades may be 90 degrees apart from its neighboringrotor blades and may be evenly distributed. The distal end of each rotorblade extends outwardly. The proximal ends of each rotor blade may berotatably connected to an actuator or a rotating shaft. Each rotor bladehas a top surface substantially facing upward in the UAV's initialtaking-off orientation (with or without a tilt angle), and a bottomsurface substantially face downward (with or without a tilt angle) whenthe top part of the UAV is facing upward. There may be a tilt anglebetween a horizontal plane and the top or the bottom surface, when theUAV is substantially in a horizontal plane. The top and bottom surfacesof each rotor blades may be sufficiently flat. The top and bottomsurfaces of each rotor blades may not be sufficiently flat that it mayhave a convex, a grove, a depression, a concavity, a protrudingstructure, a rib, or the like.

Each propulsion unit may include at least a protective cover 1606. Theprotective cover may protect the elements of the propulsion unit withinthe protective cover from damages or undesired impact from externalsources when the UAV is flying, landing, taking off, and/or changingdirections. Such elements of the propulsion unit may include all therotor blades, all the supporting structures, all actuators, all sensors,the rotating shaft, all ESCs, all flight control units therewithin. Inaddition, the protective cover may also protect the central body 1602and elements located on or within the central body from damages orundesired impact from external sources when the UAV is flying, landing,taking off, and/or changing directions. The protective cover alsoprotects the optional arms 1612 of the UAV. The height h_(pc) of one ormore protective covers may be greater than the height of the centralbody h_(b), and the central body may be positioned around the center ofheight h_(pc) of the protective cover. Similarly, the height h_(pc) ofone or more protective covers may be greater than the height of therotor blades h_(rc), and the rotor blades may be positioned around thecenter of height h_(pc) of the protective cover. Similarly the heighth_(pc) of one or more protective covers may be greater than the heightof the propulsion unit, which may be smaller or equal to the totalheight of the rotor blades and the motors. Thus, the central body may besuspended above an underlying surface and protected from touching alanding surface or external objects when the UAV is landing or crashingto a landing surface in any orientation. The central body may be alsosuspended in the front-rear direction and/or left-right direction of theUAV, so that when the UAV lands with its left, right, front, or rearside down, the central body may be free of contact with the landingsurface. In some cases, the one or more protective covers serve aslanding gears for the UAV. In some cases, the one or more protectivecovers serve as landing gears for the UAV in a first orientation, in asecond orientation, or in any other flight orientations. As examples,the top edges and/or the bottom edges of the protective cover may serveas landing stand or part of landing gear so that it touches a landingsurface and allow the other elements remain suspended from theunderlying surface. The protective cover may provide advantageous todifferent scenarios of UAV operation as it protects the rotor blades aswell as the central body. In some instances, solid protective coversprotects rotor blades from contacting tree branches or bushes when theUAV flies, thus prevent the rotor blades from trapping, stopping or evenbreaking by the tree branches or bushes. In other instances, when theUAV crash lands in an unpredictable orientation, (first left-side downthen lands tilted on a uneven surface), various portions of theprotective cover may touch the landing surface (the outer surface firstthen the bottom edge), and provide support for the entire UAV, andprotect the central body from hitting the landing surface or anyexternal objects on the landing surface. Thus, protects the central bodyand elements thereon and/or therewithin from damages or undesiredimpact. The portion of the protective cover contacting a landing surfacemay be the top edge, the bottom edge, and/or the longitudinal wall ofthe protective cover. In some instances, a UAV flips under a strong windand drops to an uneven ground upside down. The top edge of theprotective cover lands on the ground and protect the suspended centralbody.

FIG. 17 illustrates a movable object 1700 including a carrier 1702 and apayload 1704, in accordance with embodiments. Although the movableobject 1700 is depicted as an aircraft, this depiction is not intendedto be limiting, and any type of movable object can be used, aspreviously described herein. One of skill in the art would appreciatethat any of the embodiments described herein in the context of aircraftsystems can be applied to any movable object (e.g., an UAV). In someinstances, the payload 1704 may be provided on the movable object 1700without requiring the carrier 1702. The movable object 1700 may includepropulsion mechanisms 1706, a sensing system 1708, and a communicationsystem 1710.

The propulsion mechanisms 1706 can include one or more of rotors,propellers, blades, engines, motors, wheels, axles, magnets, or nozzles,as previously described. For example, the propulsion mechanisms 1706 maybe self-tightening rotors, rotor assemblies, or other rotary propulsionunits, as disclosed elsewhere herein. The movable object may have one ormore, two or more, three or more, or four or more propulsion mechanisms.The propulsion mechanisms may all be of the same type. Alternatively,one or more propulsion mechanisms can be different types of propulsionmechanisms. The propulsion mechanisms 1706 can be mounted on the movableobject 1700 using any means, such as a support element (e.g., a driveshaft) as described elsewhere herein. The propulsion mechanisms 1706 canbe mounted on any portion of the movable object 1700, such on the top,bottom, front, back, sides, or suitable combinations thereof.

In some embodiments, the propulsion mechanisms 1706 can enable themovable object 1700 to take off vertically from a surface or landvertically on a surface without requiring any horizontal movement of themovable object 1700 (e.g., without traveling down a runway). Optionally,the propulsion mechanisms 1706 can be operable to permit the movableobject 1700 to hover in the air at a specified position and/ororientation. One or more of the propulsion mechanisms 1700 may becontrolled independently of the other propulsion mechanisms.

Alternatively, the propulsion mechanisms 1700 can be configured to becontrolled simultaneously. For example, the movable object 1700 can havemultiple horizontally oriented rotors that can provide lift and/orthrust to the movable object. The multiple horizontally oriented rotorscan be actuated to provide vertical takeoff, vertical landing, andhovering capabilities to the movable object 1700. In some embodiments,one or more of the horizontally oriented rotors may spin in a clockwisedirection, while one or more of the horizontally rotors may spin in acounterclockwise direction. For example, the number of clockwise rotorsmay be equal to the number of counterclockwise rotors. The rotation rateof each of the horizontally oriented rotors can be varied independentlyin order to control the lift and/or thrust produced by each rotor, andthereby adjust the spatial disposition, velocity, and/or acceleration ofthe movable object 1700 (e.g., with respect to up to three degrees oftranslation and up to three degrees of rotation).

The sensing system 1708 can include one or more sensors that may sensethe spatial disposition, velocity, and/or acceleration of the movableobject 1700 (e.g., with respect to up to three degrees of translationand up to three degrees of rotation). The one or more sensors caninclude global positioning system (GPS) sensors, motion sensors,inertial sensors, proximity sensors, or image sensors. The sensing dataprovided by the sensing system 1708 can be used to control the spatialdisposition, velocity, and/or orientation of the movable object 1700(e.g., using a suitable processing unit and/or control module, asdescribed below). Alternatively, the sensing system 1708 can be used toprovide data regarding the environment surrounding the movable object,such as weather conditions, proximity to potential obstacles, locationof geographical features, location of manmade structures, and the like.

The communication system 1710 enables communication with terminal 1712having a communication system 1714 via wireless signals 1716. Thecommunication systems 1710, 1714 may include any number of transmitters,receivers, and/or transceivers suitable for wireless communication. Thecommunication may be one-way communication, such that data can betransmitted in only one direction. For example, one-way communicationmay involve only the movable object 1700 transmitting data to theterminal 1712, or vice-versa. The data may be transmitted from one ormore transmitters of the communication system 1710 to one or morereceivers of the communication system 1712, or vice-versa.Alternatively, the communication may be two-way communication, such thatdata can be transmitted in both directions between the movable object1700 and the terminal 1712. The two-way communication can involvetransmitting data from one or more transmitters of the communicationsystem to one or more receivers of the communication system 1714, andvice-versa.

In some embodiments, the terminal 1712 can provide control data to oneor more of the movable object 1700, carrier 1702, and payload 1704 andreceive information from one or more of the movable object 1700, carrier1702, and payload 1704 (e.g., position and/or motion information of themovable object, carrier or payload; data sensed by the payload such asimage data captured by a payload camera). In some instances, controldata from the terminal may include instructions for relative positions,movements, actuations, or controls of the movable object, carrier and/orpayload. For example, the control data may result in a modification ofthe location and/or orientation of the movable object (e.g., via controlof the propulsion mechanisms 1706), or a movement of the payload withrespect to the movable object (e.g., via control of the carrier 1702).The control data from the terminal may result in control of the payload,such as control of the operation of a camera or other image capturingdevice (e.g., taking still or moving pictures, zooming in or out,turning on or off, switching imaging modes, change image resolution,changing focus, changing depth of field, changing exposure time,changing viewing angle or field of view). In some instances, thecommunications from the movable object, carrier and/or payload mayinclude information from one or more sensors (e.g., of the sensingsystem 1708 or of the payload 1704). The communications may includesensed information from one or more different types of sensors (e.g.,GPS sensors, motion sensors, inertial sensor, proximity sensors, orimage sensors). Such information may pertain to the position (e.g.,location, orientation), movement, or acceleration of the movable object,carrier and/or payload. Such information from a payload may include datacaptured by the payload or a sensed state of the payload. The controldata provided transmitted by the terminal 1712 can be configured tocontrol a state of one or more of the movable object 1700, carrier 1702,or payload 1704. Alternatively or in combination, the carrier 1702 andpayload 1704 can also each include a communication module configured tocommunicate with terminal 1712, such that the terminal can communicatewith and control each of the movable object 1700, carrier 1702, andpayload 1704 independently.

In some embodiments, the movable object 1700 can be configured tocommunicate with another remote device in addition to the terminal 1712,or instead of the terminal 1712. The terminal 1712 may also beconfigured to communicate with another remote device as well as themovable object 1700. For example, the movable object 1700 and/orterminal 1712 may communicate with another movable object, or a carrieror payload of another movable object. When desired, the remote devicemay be a second terminal or other computing device (e.g., computer,laptop, tablet, smartphone, or other mobile device). The remote devicecan be configured to transmit data to the movable object 1700, receivedata from the movable object 1700, transmit data to the terminal 1712,and/or receive data from the terminal 1712. Optionally, the remotedevice can be connected to the Internet or other telecommunicationsnetwork, such that data received from the movable object 1700 and/orterminal 1712 can be uploaded to a website or server.

While some embodiments of the present disclosure have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the present disclosure. It should beunderstood that various alternatives to the embodiments of the presentdisclosure described herein may be employed in practicing the presentdisclosure. It is intended that the following claims define the scope ofthe present disclosure and that methods and structures within the scopeof these claims and their equivalents be covered thereby.

1. A method of operating an unmanned aerial vehicle (UAV) comprising:generating, with aid of one or more processors, a signal that causes theUAV to flip from a first orientation to a second orientation opposite tothe first orientation; and effecting, with aid of one or more propulsionunits, flip of the UAV from the first orientation to the secondorientation in response to the signal.
 2. The method of claim 1, whereinthe UAV is flipped from the first orientation to the second orientationopposite to the first orientation while the UAV is on an underlyingsurface.
 3. The method of claim 2, further comprising: obtaining dataindicative of a user input to initiate the flip of the UAV from thefirst orientation to the second orientation, the user input beingreceived at a terminal remote to the UAV via a wireless connection. 4.The method of claim 2, further comprising: obtaining data from one ormore sensors to initiate the flip of the UAV from the first orientationto the second orientation, the one or more sensors being on-board theUAV and configured to detect an orientation of the UAV.
 5. The method ofclaim 2, wherein: the first orientation of the UAV is upside down; orthe second orientation of the UAV is right side up.
 6. The method ofclaim 2, wherein the UAV includes: one or more protectors that preventthe one or more propulsion units from directly contacting the underlyingsurface.
 7. The method of claim 2, wherein the UAV is on the underlyingsurface for at least a moment in time after flipping to the secondorientation.
 8. The method of claim 2, further comprising: effecting,with aid of the one or more propulsion units, takeoff of the UAV fromthe underlying surface subsequent to the flip of the UAV from the firstorientation to the second orientation.
 9. The method of claim 8, furthercomprising: effecting flight of the UAV in the second orientation. 10.The method of claim 1, wherein: generating the signal includesgenerating the signal in response to one or more sensors detecting thatthe UAV has reached a threshold condition.
 11. The method of claim 10,wherein the threshold condition includes at least one of: an altitude ofthe UAV with respect to an underlying surface, a velocity oracceleration of the UAV with respect to the underlying surface, powerprovided to the one or more propulsion units, power consumed by the oneor more propulsion units, or an amount of time that has elapsed sincethe UAV has taken off from the underlying surface.
 12. The method ofclaim 1, wherein the signal is indicative of: a user input to initiatethe flip of the UAV, the user input only initiating the flip and noother actions by the UAV, or a single action that effects the flip ofthe UAV from the first orientation to the second orientation.
 13. Anunmanned aerial vehicle comprising: one or more processors, individuallyor collectively configured to generate a signal that causes the UAV toflip from a first orientation to a second orientation opposite to thefirst orientation; and one or more propulsion units configured to effectflip of the UAV from the first orientation to the second orientation inresponse to the signal.
 14. The UAV of claim 13, wherein the UAV isflipped from the first orientation to the second orientation opposite tothe first orientation while the UAV is on an underlying surface.
 15. TheUAV of claim 14, wherein the one or more processors are furtherconfigured to: obtain data indicative of a user input to initiate theflip of the UAV from the first orientation to the second orientation,the user input being received at a terminal remote to the UAV via awireless connection.
 16. The UAV of claim 14, wherein the one or moreprocessors are further configured to: obtain data from one or moresensors to initiate the flip of the UAV from the first orientation tothe second orientation, the one or more sensors being on-board the UAVand configured to detect an orientation of the UAV.
 17. The UAV of claim14, wherein the one or more propulsion units are further configured to:effect takeoff of the UAV from the underlying surface subsequent to theflip of the UAV from the first orientation to the second orientation.18. The UAV of claim 17, wherein the one or more propulsion units arefurther configured to: effect flight of the UAV in the secondorientation.
 19. The UAV of claim 13, wherein the UAV is flipped fromthe first orientation to the second orientation opposite to the firstorientation in response to one or more sensors detecting that the UAVhas reached a threshold condition.
 20. The UAV of claim 19, wherein thethreshold condition includes at least one of: an altitude of the UAVwith respect to the underlying surface, a velocity or acceleration ofthe UAV with respect to the underlying surface, a vertical velocity oracceleration of the UAV with respect to the underlying surface, powerprovided to the one or more propulsion units, power consumed by the oneor more propulsion units, or an amount of time that has elapsed sincethe UAV has taken off from the underlying surface.